STOKES COLLECTION OF ANTARCTIC FOSSILS 417 



All of the Antarctic specimens are sinistral; in the original description the species is 

 said to be usually sinistral, but some of Ihe Indian specimens are dextrally coiled and 

 in a larger collection from Antarctica both forms of shell would doubtless be dis- 

 covered. The species is also somewhat closely allied to T. pupoides Stanton, from 

 the Cretaceous beds of Patagonia. 



CEPHALOPODA. 



Olcostephanus antarctica, n. sp. Plate II, Figs. 1-2. 



Description. — Shell discoid, compressed, dorsum regularly rounded, the 

 aperture two-thirds as broad as high. Umbilicus of moderate size with nearly 

 vertical sides, leaving about three-eighths of the inner whorls exposed. Sur- 

 face of whorls marked by sharply elevated transverse ribs which are continu- 

 ous uninterruptedly across the dorsum, their crests being from two to three 

 millimeters apart ; most of these ribs originate in a row of tubercles upon 

 the edge of the umbilicus, each tubercle giving rise to two or three ribs, but 

 between the ribs originating in this way there are others which start on the 

 edge of the umbilicus between the bases of the tubercles. The crest of each 

 rib is surmounted by a row of small, low, tubercles about two millimeters 

 apart. 



The maximum diameter of the type specimen is 68™", the height of the 

 aperture 30™™. and the width of the aperture 20""". 



— Walker Museum Pall. Coll. No. 9706. 



Remarks. — This type of Ammonite shell, with strong lateral ribs which usually 

 originate in fascicles from nodes on the border of the umbilicus and continue uninter- 

 ruptedly across the dorsum, is uncommon in the Cretaceous faunas of North America, 

 where it is recognized only in beds of Neocomian or Lower Cretaceous age on the 

 Pacific coast. In Europe the genus is restricted to the Upper Jurassic and Lower 

 Cretaceous. The antarctic species here described, however, is not closely similar to 

 any of the American or European species of the genus, but is allied to several species 

 of Ammonites {A. kaliki Stoliczka, A. madrashius Stoliczka, and A. bhawani 

 Stoliczka),' from the Middle Cretaceous beds of Southern India, all of which should 

 probably be referred to the genus Olcostephanus. O. antarctica may be distinguished 

 from all of the Indian species, however, by the line of low tubercles which surmounts 

 each one of the lateral ribs of the shell. 



Haploceras? sp. undet. Plate II, Fig. 5. 



A single distorted and imperfect specimen of a cephalopod with all the 

 inner whorls destroyed, may be referred to the genus Haploceras with a 

 query. The surface of the shell is smooth, the dorsum rounded, with the lat- 

 eral surfaces gently convex and rounding rather abruptly into the umbilicus 

 ■which IS of moderate size. So far as can be determined the margin of the 

 aperture is continuous, not being produced forward on the sides and on the 

 dorsum, but the specimen is not in a condition to show the form of the aper- 

 ture with certainty. None of the sutures are preserved. 



'^Pal. Ind., "Foss. Ceph. of Cret. of S. India." 



