p. 213-218 ; 24 cm.Includes bibliographical references

Allen, J. A. (Joel Asaph), 1838-1921.

Batty, Joseph H., d. 1906.

Goldman, Edward Alphonso, 1873-1946.

Nelson, Edward William, 1855-1934.

American Museum of Natural History Scientific Publications

Article XV.-DESCRIPTIONS OF TWO NEW OPOS-SUMS OF THE GENUS METACHIRUS.By J. A. ALLEN.The Opossums of the genus Metachirus of Mexico and CentralAmerica had been referred to D. quica of Temminck, the typelocality of which is the coast region of southeastern Brazil (cf.Allen, this Bulletin, XIII, I900, p. 195), until in October of lastyear I separated the Central American form as Metachirus fus-cogriseus (Z. C., p. I94), on the basis of a specimen supposed tohave come from Colon. Through the kindness of Dr. C. HartMerriam, Chief of the Biological Survey, U. S. Department ofAgriculture, I have recently had opportunity to examine largeseries of specimens from Nicaragua and various localities inMexico, numbering altogether 42 specimens. As probably nolarge series of examples of the genus Metachirus has ever beforebeen brought together, it seems desirable to give a somewhatdetailed account of this important collection.Metachirus fuscogriseus Allen.M3fe(achirus fuscogriseus ALLEN, Bull. Am. Mus. Nat. Hist., XIII, I900, p.194.A number of specimens from Greytown and Bluefields, Nica-ragua, agree well with the type of this species, supposed to havecome from a point somewhat further south on the coast. Thereis, therefore, little to add to the original description of the speciesbeyond noting the variations in the specimens of the presentseries due to age, season, etc.The present material consists of 4 specimens, two adult malesand two adult females, collected at Greytown, Feb. 7-10, i892, byDr. C. W. Richmond, now Assistant Curator of Birds at the U. S.National Museum; and 3 adults, 3 young adults, and 5 half-grownyoung, collected 50 miles above Bluefields on the EscondidoRiver at various dates from May to November of the same year,also by Dr. Richmond, making in all I5 specimens from these twolocalities.Three of the Greytown specimens are quite uniform in colora-tion, while the fourth is of a duller, browner black above andmore strongly buffy below. The Bluefields adult and young[213]2 I4 Bulletin American Museum of Natural History. [Vol. XIV,adult specimens are similar in coloration to those from Greytown,except in the case of one very old male, distinguished by its largesize and a strong orange-rufous tinge on the cheeks, sides of theneck, and throat. This series shows, as in the case of Didelphis,that the animal increases greatly in size after reaching maturity.In the younger specimens the buff color of the ventral surface isrestricted to the chest and the lower abdominal region, the twoareas being connected by a narrow buffy median band, the sidesof the abdomen being more or less plumnbeous, with the tips of thehairs lighter, a condition often seen in various species of Murida,especially in Neotoma, Oryzomys and allied genera. The adultmales are distinguished in the breeding season by a pale yellowishpatch on the sides of the lower abdomen just in front of thethighs, the corresponding area in the female being whitish, andthe hair at these points is of a little different texture from that ofthe surrounding parts.EXTERNAL MEASUREMENTS.C;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.bODLOCALITY. ,Cu11w Greytown,Nicaragua...................... 586 282 304 45 108& 530 257 273 40 207+ 529 262 268 41.5 103*t...........I.......... 53I9 245 274 40 I 2I2Near Bluefields,l Nicaragua............... 8 625 305 320 46 20550877" 6 .............. ~562 265 '297 41 11352380 " .............. 5I8 243 275 41 113Average, 3 males ......... 580 282 299 44 io64 females.................. 532 254 279 41 Io0.81 Fifty miles from Bluefields, on the Escondido River.MEASUREMENTS OF SKULLS.Nasals. Palate._~~~~~~~( 0o LOCALITY. 0 My Cu 0.Z - . 0 . 4 0 40 Cu C) C . 0 00 0flt Greytown, Nicaragua & 77.3 65 34.6 9 5 38.5 24.3 9 23 40 2I.426 2450887Blefields,66i6 32.3 8 4 34.5 24.5 9 22.5 39 20 25 2450887 Bluefields, $ 6 60 33.5 6 5 33 22 9 28.5 38 20 25.3113.651442 79 70 36 9 5.6 40.5 I5 8.3 24 43 22 25 24I9OI.] AlZen, New Opossums of the Genus Metachirus. 2 I 5Metachirus fuscogriseus pallidus, subsp. nov.Type, No. 58158, U. S. Nat. Mus., 8 acldlt, Orizaba, Vera Cruz, Mexico,June 24, I894. Collected by E. W. Nelson and E. A. Goldman.Similar to M. fuscogriseus, but the coloration is much lighter, the eye spotsare larger, and the black of the head less intense and more restricted in area pos-teriorly; size and proportions apparently the same as in fuscogriseus;Measurements.-Type: Total length, 627; head and body, 315; tail, 312;tarsus, 47 (collector's measurements in the flesh). The skin measurements showdifferent proportions. While the total length is the same as above given, thelength of the head and body is 310, and of the tail 317, which would give aboutthe normal tail ratio. For further measurements see table of measurementsbelow.Skull.-The skull presents no appreciable difference from skulls of corre-sponding age of M. fuscogriseus from Nicaragua. The measurements of thetype skull are as follows: Total length, 77; basal length,' 69; length of nasals,37; zygomatic breadth, 39; postorbital processes, 14.3; postorbital constric-tion, 9; mastoid breadth, 25; palatal length, 42; palatal breadth at mm4(including teeth), 22.5 ; upper toothrow, 27; upper molar series, I5. Thespecimen selected for type is much above average size, as shown by the measure-ments tabulated below.EXTERNAL MEASUREMENTS.Nat. Mus. LOCALITY. Sex. Total and Tail. Tarsus. TailNo. Length . bodTay. arus ratio.0OOI89 Montecristo, Tabasco, Mex...........3 555 267 288 44.5 i08I00028 Frontera, .......... a 556 265 291 46 Ilo100027 508 254 254 43.5 I00100034 Teapa, .......... 585 275 310 47 11I00031 .. .......... 582 280 302 47 107100033 .. .... ...it542 253 289 43*5 2IO100032 it.............. . 542 254 288 41 .5 I1I2100030 .............9 505 241 264 41 109.5100029 8..........r 265 293 43 IIO77908 Huehuetan, Chiapas, " 545 264 28I. 46 Io678003 Chicharras, .......... 524 254 270 43 Io658158 Orizaba, Vera Cruz, .......... 627 315 312 47 0958157 .......... 490 250 240 38 9663664 Montzorongo 488 220 260 40 iI865403 Tuxtepec, Orizaba, :'. 58o 265 315 46 11965404 3......a 580 280 300 45 10792992 Metlaltoyuca, Puebla, 3557...... 5 240 277 43 115.492993 3..... 527 245 282 44 311592994 "s.......... a.......... t578 298 280 48 9492995 .. .......... a 585 283 302 46 106.792992 .......... y 475 222 253 40 114Teapa, etc., Tabasco, 43 569- 5 272 298 46 IogAveraged 599 535 254 277.6 42.5 108.3Tuxtepec, Orizaba, 2 3 3 58o 272.5 307.5 45.5 213LMetlaltoyuca, Puebla, 48 8 552.5 266.5 285 45.2 110.31 From posterior base of incisors to front border of foramen magnum.2I6 Bulletin AmericaAMuseum of Natural History. [Vol. XIV,MEASUREMENTS OF SKULLS.SzLOCALITY.CUz58I56 Orizaba,Vera Cruz,Mex.58258 " "& A.63663 Chichicaxtle,"65405 Catemaco,63664 Motzorongo,93002 Papantla, "93002 I65404 Tuxtepec, Oaxaca,77908 Huehuetan,Chiapas,78003 Chicharras,92991 Metlaltoyuca.Puebla"92992929939299492995200027 Frontera, Tabasco,200030 Teapa,2000322000332000312200028 Frontera, "NASALS.bO 4 110374 62 36 8 5S 77 69 37 9.3 53 72.3 65.5 34 8 4.5973 67 34 8 4.3960 55 28 7 3 .53 64 575 30 7 4.5S 64.-557-5 30 6.6 4a 69 6I.5 32 7.6143 69 61.7 32 7.3149 67 59 33 17.5 4.2S6I 54 27 i7 3-43 62 57 30.2 7.5 43 6I.6 60 30 6.5143 74.3 68 35 i8.2 5.43 69 63.5 33 17 49166.3 6r 32.2 8 4-3164.5 59 29 !7 463 57.5 30.5 7.21464 58.4 30.2 7 4a 74 5 67.5135.5 8 5170 63 135 7.3 4.3This pale northern form of Metachirus fuscogriseus is repre-sented by a considerable number of specimens from the States ofTabasco, Vera Cruz, Oaxaca, and Puebla. They vary a littlein coloration above, some being darker than others, but the dif-ference is slight and partly seasonal. he lower surface variesin general tone from yellowish white to deep buffy white. Youngspecimens show gray areas on the sides of the abdomen, as in M.fuscogriseus. All the adult mnales show more or less strongly asulphur yellow patch on the sides of the abdomen in front of thethighs, this tint varying from pale yellowish to strong greenishyellow. Several specimens differ from the average style throughthe intensity of the buff coloration on the throat and sides of theneck which tint sometimes prevails as a strong bu-ff wash overmost of the lower surface. The greenish yellow patch in front ofthe thighs is characterized by a slightly different texture of thehair, and is represented in the female by a clearer white than thesurrounding parts. Apparently it is a glandular area, andmost active in the breeding season, corresponding doubtlessto the glandular area on the lower throat and chest in Didelphis.4.0j.0N32.5393837303232.5343532.23033324'35 53332.332333835C.;040~02324.32423.510.522.322.322.522.712051227IO2 .220.5I61212II .411I.2IO .71312 .50.o o0X 1.'09 249 258.5 22.38.5 22.58. 5x88.6 198.5 I98. 3 28.2 208.4 208 I8.28.7 29.58.2 209 238.5 228.5 208 208 29.58.2 29.58 22I7 12PALAI E-040 21 2542 22 .5 2740 20. 2540 21 2635 x8f 123-336 i9.512536 I19.5 2438 21 25.339 20 25 538 29 2434 19 2336 20 23 538 20 24.643 21 2439 2I 2538 20 253743 20 2536 11I9 .7 12436 20 23.541 21 2639.5 20 25.502425I3.524.3232413-3o23.3242423.523235I31324213.623.21324.21419oi.] Allen, New Opossums of the Genus Metachirus.As shown in the tables of measurements, there is considerablevariation in size, and some in proportions, in animals that havereached matturity, measurements being given of no specimens inwhich the last molar has not come into use, with other evidencesof maturity. The largest specimen, which has perhaps unfortu-nately been taken for the type, is equalled in size by a singlespecimen from Greytown, also an old male. The ratio of lengthof tail to length of head and body varies in specimens from thesame locality, as at Metlaltoyuca, Puebla, from 94 to I I5, with atotal range of variation in this respect from 94 to iI9, the aver-age being IO9. In young and middle-aged skulls there is barelya trace of a sagittal crest, but in old males it attains a height of2 to 3 mm. The postorbial processes are but slightly developedin early life, reaching only a moderate development even in oldage. The postorbital constriction is much less than in theallied genus Dideiphis, to which in many respects the skull isclosely similar. The nasals, however, are more pointed, bothposteriorly and anteriorly, terminating at both extremities in at-tenuated points. The large series from Teapa and Frontera,Tabasco, appear not to show any average difference, either incoloration or size, from specimens from Metlaltoyuca, Puebla,and further subdivision of the material seems at present un-necessary.Metachirus grisescens, sp. nov.Type, No. 15072, Am. Mus. Nat. Hist., ? adult, Rio Cauca, Colombia,June, I899; J. H. Batty.Somewhat similar to Metachirus fuscogriseus pallidus, but much palerthroughout with the tail uniform dark brown, not light at the tip as in the M.fuscogriseus group. General coloration above gray, varied with black; belowwhitish, with a slight buffy suffusion; eye spots and head markings as in M.fuscogriseus, the black, however, less intense, and much less extended pos-teriorly. While the general coloration above is blackish varied with gray inM. fuscogriseus, in the present species it is gray varied with blackish.Measurements (from the dried skin).-Total lebgth, 510; head and body,260; tail, 240; tarsus, 38; tail ratio, about 9I. These measurements are onlyapproximate, as the tail is not wholly filled out and the specimen is not wellprepared, the skin evidently being much shrunken. The ears are small, about20 by I7 mm. in the dry skin.Skull.-The skull differs from that of Metachirus fuscogriseus in the greatexpansion of the posterior portion of the nasals, which maintain a uniform21 72 I 8 Bulletin American Museum of Natural History. [Vol. XIV,breadth for about 4 mm. beyond the point of greatest expansion, then tapersuddenly and end abruptly, instead of converging evenly to a slender point.The palatal vacuities are also unusually developed, as much so as is ordinarilythe case in DideMpkis. The skull is large for the size of the skin, which issexed by the collector as a female. Total length, 68; basal length, 62; lengthof nasals, 33 ; zygomatic breadth, 36 ; postorbital processes, I5; postorbitalconstriction, 9; mastoid breadth, 37.6 ; breadth across mm I,I9.5; length ofupper toothrow, 23 ; upper molar series, I3.This species is based on a single specimen from Rio Cauca,Colombia, collected by Mr. J. H. Batty, June, I899. It differsfrom the Mexican and Central American forms in its very lightcoloration and in the tail being uniformly blackish brown with-out the usual light tip. The skull is peculiar for a member ofthis genus in the large size of the palatal vacuities and in thegreat breadth of the posterior third of the nasals, which havemore the form of the nasals in M. nudicaudatus. It differs, how-ever, from this species through its much larger size and differentcoloration, and in the basal two inches of the tail being furred.BULLETIN A. M. N. H.THE FE4ERAL ALBSERTYPE CO., NEW YORK.''''ii. %,HELICOCERAS STEVENSONI, N. SP.Front View, Nat. Size.PL. XXIX.BULLETIN A. M. N. H.ITHE FEDERAL AL8ERTYPE CO., NEW YORKHELICOCERAS STEVENSONI, N. SP.Back view, Nat. Size.PL. XXX.

New opossums of the genus Metachirus

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