NATJTILOIDEA. 69 



VL -CEPHALOPODA. 

 1. Order : NAUTILOIDEA. 



Family: ^AVTILWM. 



Genus: NAUTILUS, Breyn. 



Nautilus subl^vigatus, d'Orbigny. PI. XIX, fig. 1-la, 2-2a ; PI. XX, 



fig. 1-la, 2.2b. 



1840. Nautilus Itevigatut, d'Orb., Pal. Franc. Ter. Crdt., Vol. I, p. 84, pi. 17. 



1850. Nautilus suUceoigatus, d'Orbigny, Pal. Franc. Ter. Cret., Vol. II, p. 189. 



1854. Nautilus lahechi, d'Archiac and Haime, Descr. des Anim. foss. du Groupe Numm. de I'Inde, cage 



338, pi. XXXIV, fig. 13, a. b. 

 1865. Nautilus suhlavigatus, Stoliczka, Cretaceous Fauna of Southern India, Cephalopoda, page 203, 

 pi. V, figs. 1 & 3. 



I. 



Diameter of the shell 114 mm. 



.. „ umbilicus 11 „ 



Height of the last whorl from the umbilical suture . . (?) 69 „ 

 „ „ „ „ preceding whorl . ? 



Thickness of the last whorl 84 „ 



Number of septa to one volution (P) 36 



The subglobose shell is composed of highly inflated whorls which overlap each 

 other to such an extent that only a narrow but deep umbilicus remains. The 

 remarkable feature of this species consists in the rapid lateral expansion of the body 

 chamber towards its end, so that the shell attains its greatest thickness at the aper- 

 ture of the body chamber. The ventral side is rounded, the sides slope moderately 

 from the umbilical edge towards the ventral side, into which they gradually pass. 



The septa follow each other rather closely and appear nearly straight, exhibit- 

 ing only a slight sinus on the flanks. The siphuncle is eccentric, very close to the 

 dorsal sidfe. The thin shell is covered with fine striae of growth, which from their 

 direction apparently indicate the existence of rather a deep ventral sinus at the 

 end of the body chamber. 



Locality and stratigraphical position.— Mazav Drik ; D6s valley. 



Remarks. — Messrs. d'Archiac and Haime have described four species of the 

 genus Nautilus from the •* chaine de Hala." According to Dr. Blanford, Nautilus 

 labechi only is found with certainty in cretaceous beds, while it seems rather 

 doubtful whether Nautilus suhfieuriausianus and Nautilus forbesi occur in the 

 same beds. All of them, including Nautilus deluci, are found in the Eanikot beds ; 

 Nautilus labechi is even said to ascend to the Khirthar beds. Under these circum- 

 stances it seems important to compare the Baluchistdn specimens with those from 

 Sind, and as the result of this comparison I can assert that whatever the specific 

 value of the form here described as Nautilus sublcevigatus may be, it is certainly 

 identical with the Nautilus labechi from Sind. 



Messrs. d'Archiac and Haime's figure is not a good one, inasmuch as it does 

 not exhibit the characteristic expansion of the shell at the end of the body chamber 



