Trace fossils from two Upper Pennsylvanian sandstones in Kansas

14 p., 5 pl., 3 fig.http://paleo.ku.edu/contributions.htm

Isopod and limulid marks and trails in Tonganoxie Sandstone (Upper Pennsylvanian) of Kansas

10 p., 4 pl.http://paleo.ku.edu/contributions.htm

Mesozoic ammonites

21 p. : ill. ; 26 cm.Includes bibliographical references (p. 21)."The first few septa and associated structures in the early whorls of Mesozoic ammonites were studied in a number of genera including Quenstedtoceras, Kosmoceras, Euhoplites, Hypacanthoplites, Baculites, and Scaphites and its related genera. Exceptionally well-preserved specimens with little obscuring matrix inside permitted observations of the spatial arrangement of the first few septa and were supplemented by sections polished parallel to the median plane. Our observations indicate that: 1. The proseptum is a single structure and does not consist of two septa. Prismatic attachment deposits of the caecum and siphuncle occur around the proseptal opening. 2. In all genera except Quenstedtoceras, the second septum is moderately distant from the proseptum and, in median section, is slightly convex, not concave, toward the aperture. In Quenstedtoceras, however, the second septum grows dorsally into the proseptum and is only conspicuous on the venter. These relationships are also expressed in the shape and spacing of the corresponding sutures on steinkerns of the initial whorls. 3. In all genera in which the original shell structure was preserved, the second septum is nacreous, not prismatic. Therefore, in agreement with Drushchits and Khiami (1970), we prefer the simpler terms second septum and third septum for primary septum and nacroseptum, respectively. 4. The development of a prismatic attachment ridge at the base of the proseptum, dorsal muscle scars just adoral of each septum, and wrinkles in the proseptum and prosiphonal attachment sheets support the model of early ammonite ontogeny proposed by Bandel (1982)"--P. [1]

Integrated frequency comb laser with narrow intrinsic optical linewidth based on a dielectric waveguide feedback circuit

We present an integrated hybrid semiconductor-dielectric (InP-Si$_3$N$_4$) waveguide laser that generates frequency combs at a wavelength around 1.5 $\mu$m with a record-low intrinsic optical linewidth of 34 kHz. This is achieved by extending the cavity photon lifetime using a low-loss dielectric waveguide circuit. In our experimental demonstration, the on-chip, effective optical path length of the laser cavity is extended to 6 cm. The resulting linewidth narrowing shows the high potential of on-chip, highly coherent frequency combs with direct electrical pumping, based on hybrid and heterogeneous integrated circuits making use of low-loss dielectric waveguides

Cassiopid gastropods from the cretaceous of Western Serbia

Three species of Cassiopidae (Cerithioidea, Gastropoda) are described from outcrops in the vicinity of the villages Rastište and Mokra Gora in western Serbia. They occur in marly limestones of near shore shallow water deposits. Earlier micropaleontological investigations have indicated an Albian-Cenomanian age. The species encountered are related to those present in deposits of the European margin of the Tethys and closest relationships exist to those of the Armenian and Transcaucasian region. Our species can be placed in the genera Cassiope, Paraglauconia and Bicarinella. A new species Cassiope kotromanensis is erected. Assumptions about post-mortem shell transport and size sorting of gastropod shells were examined through statistical analysis

Die Embryonalentwicklung von Hibolithes (Belemnitida, Cephalopoda)

A study of unaltered minera·l shell la yers, the reconstruction of the organic layers and a comparison with the embryonic shells of other shell-bearing cephalopods indicate that the young Hibolithes hatching from the egg was a miniature adult. In contrast to other known siphunculate cephalopods a siphunclc was not yet developed at this stage, so that the first chamber was emptied by the tissue of the p03terior visceral mass.Der Entwicklungsverlauf eines Hibolithes bis zum Schlüpfen und während der Jugend wurde rekonstruiert. Dies wurde durch die Analyse der unveränderten mineralischen Schichten ,sowie die Wiederherstellung der organischen Lagen ermöglicht und im Vergleich zu Embryonalgehäusen lebender schalentragender Cephalopoden und der fossilen Ammoniten gedeutet. Der Schlüpfling ähnelt einem erwachsenen Tier, hatte allerdings noch keinen Sipho entwickelt, sondern pumpte die erste Kammer über ein organisches Septum mit dem Gewebe des rückwärtigen Eingeweidesackes leer. Erst während des freien ]ugendlebens wurde ein Sipho differenziert