CRETACEOUS FOSSILS. 141 



The same author anticipated the occurrence of this genus, as will be seen by 

 consulting the analytical table of the group in Part 3, Paleontologie Suisse. He 

 defines the three allied genera thus : 



" Une spire composed de tours disjoints, et une crosse. Ancyloceras." 



" Portion spirale tres courte et irreguliere, a tours tres-ecartes, une tres-grande 

 crosse comprise dans une plan. Anisoceras." 



" Spire reguliere d' Helicoceras terminee par une crosse. Cas possible non encore 

 observe." 



There is one character, to which attention has been called, both by this author 

 and by Dr. Stoliczka, in Palseontologia Indica, which, if found to be constant in 

 Anisoceras, will serve as a good means of distinguishing the two genera; I fear, 

 however, that a generalization on this point may yet be premature. I refer to 

 the style of the septum. Pictet defines his genus as possessing six lobes and six 

 saddles, the two laterals being bifurcated and nearly equal. Stoliczka more properly 

 reduces the number to five, and speaks of the ventral as being rather a lobule than 

 a distinct ventral lobe, on account of its small size and simple ornament in all 

 the species yet examined. The present species has six lobes, the ventral being 

 normally large, and the lateral being deeply trifurcate, the inferior lateral not 

 more than half the length of the superior ; thus resembling much more the style 

 of Ancyloceras than Anisoceras. 



Among the species referred to Anisoceras, and yet but imperfectly known, there 

 are some that seem open to the suspicion of belonging in the present group. The 

 most marked case is perhaps Hamites tenuisulcatus, Forbes, Ancyloceras id., d'Orb., 

 Anisoceras id., Stol. The figure of the spiral portion in Pal. Ind., Vol. 3, pi. 85, 

 fig. 14, certainly looks like our genus, and there seems to be nothing incompati- 

 ble with this view, in the figure by Forbes in the Geol. Transactions. Its septum 

 is as yet unknown. 



H. .equicostatus, Gabb. 



PL 25, Fig. 20 a—g. 

 (Plychoceras cequicostatus, Gabb ; Pal. Cal., Vol. 1, p. 74, pi. 13, fig. 20.) 



Shell rather small ; spiral portion with the spire low, the 

 height being about equal to twice the thickness of the outer 

 volution; whorls increasing very gradually in size, nearly in 

 contact; number of whorls unknown, but from the rate of 

 increase in diameter, about four or five (one and a half pre- 

 served) ; the straight limb was apparently about twice as long as 

 the diameter of the spiral ; the larger terminal limb seems to 



