AMMONOIDEA. 71 



The septa are numerous and follow each other very closely ; I he suture line is 

 slightly curved, exhibiting a moderately deep but broad lobe on the sides, and a 

 broad, flat, ventral saddle. The siphuncle is eccentric, nearer the dorsal than the 

 ventral side, about one third of the way along the dorso- ventral line. 



The body chamber measures about half a volution, and does not expand at 

 its end. 



The shell is moderately thick, smooth, and covered with numerous ill defined 

 striae o£ growth, the direction o£ which indicates the existence of a deep ventral 

 sinus at the mouth of the body chamber. 



Locality and stratigraphical position. — Mazar Drik ; D^s valley. 



Memarhs.—Tlhe species here described is easily distinguishable from the foregoing 

 one by its less globose and laterally compressed shell — a character which is best ex- 

 hibited in the cross section. In Nautilus sublcevigatus the lateral height and thick- 

 ness exceeds the ventro-dorsal height, while in Nautilus suhfleuriausianua the op- 

 posite takes place. The cross section of the former is nearly semicircular, while it 

 is sagittate or ovate in the latter. The body chamber of Nautilus subfleuriamianus 

 never expands like that of Nautilus sublcevigatus, which is another distinguishing 

 feature. 



I have compared specimens from Sind with those from Bali^chistdn, and have 

 proved the identity of the two forms. It seems noticeable, that in Sind as well as 

 in Baluchistan, Nautilus subfleuriausianus is the rarer species of the two. 



I agree with Messrs. d'Archiac and Haime that this species is very closely 

 related to Nautilus fleuriausianus, d'Orbigny, which differs, however, by a still more 

 compressed shell and a narrower, less rounded, ventral side. 



Stoliezka^ has described as Nautilus fleuriausianus a form from Southern 

 India which, although being somewhat defective, is most probably identical with 

 d'Orbigny's species. In fact, Stoliczka seems to have expressed his doubts by de- 

 scribing it as a variety of this species. But whatever its specific value may be, it is 

 certain that it differs from Nautilus subfleuriausianus in the shape of the ventral 

 side ; although rounded on the earlier whorls, it is clearly seen on Stoliczka's 

 original that the ventral side becomes more accuminate, a blunt but distinct keel 

 gradually forming — a feature wlaidh has apparently not been noticed by Stoliczka. 



Pamily; AMMONITIBu^. 

 2. Order: AMMONOIDEA. 



Genus : INDOCERAS, gen. nov. 



In. 1876 Meek* established the genus Flacenticeraa for a remarkable group 

 of cretaceous ammonites, which he subdivided into two subgenera, Flacenticeras 



* Cretaceous Ceplialopods of Southern India, page 207. 



* Report of the United States Geological Surrey of the Territories, Vol. IX, p. 46S. 



