528 Contributions to Invertebrate Palaeontology. 



CEPHALOPODA. 



Genus TREMATOCERAS Wliitf. 



Ann. N. Y. Acad. Sci., March, 1882, p. 205. 



A straight, ohconical, cephalopodous shell, presenting the characteristics of 

 an Orthoceras, so far as the appearance of the tube, septa and siphuncle is con- 

 cerned ; but with the additional feature of a line of elongated, raised tubercles 

 along one side of the shell, which have formed perforations at certain stages of 

 growth, probably confined to the outer chamber as openings, which were closed 

 as the animal extended the shell, and before the septa opposite them were 

 formed. Type, T. Ohioonse. 



The shell for which the above generic name is proposed offers an 

 entirely novel feature among the Orthoceraticloe. The line of nodes 

 seen on the cast of the shell is entirel}^ different from anything per- 

 taining to the ornamentation of the shell, and presents the same 

 appearance as would the partially filled perforations of a Haliotis, 

 or like those shown on the back of species of Bucania, and those 

 on which the genus Tremanotus was founded ; neither is it a fea- 

 ture at all dependent upon the position of the siphon or directly 

 connected with it ; for in the specimen used the siphon is slightly 

 excentric, on the opposite side of the tube from the nodes. Its posi- 

 tion would thus indicate that it was a feature pertaining to the dor- 

 sal lip of the shell, corresponding to the sinus seen in the lip of many 

 other genera. Taking this view of it, it would appear to indicate 

 the existence of a deep, narrow notch, with raised margins, in the 

 lip of the shell at stated periods, beyond which the shell was again 

 united for a time, leaving a perforation to be closed by a deposit of 

 shell from the mantle as it approached the lower part of the chamber 

 of habitation. Many species of Orthoceras have been observed, 

 having a raised line, or rather markings, along the dorsal side ; but 

 none, so far as I am aware, presenting these evidences of a series 

 of separate openings, which I consider a feature worthy of generic 

 distinction. 



Ti'eniatoceras Oliioeiise. 



Plate X, figs. 3 and 4. 



Trematospira Ohioense Whitf., Ann. N. Y. Sci., March, 1882, p. 206. 



Shell of medium size, straight, and somewhat rapidly tapering from below 

 upward ; the rate of increase being (^qual to nearly one-sixth of the increase 

 in length. Septa moderately concave, rather closely arranged ; five of the 



