282 



Plate 32, " haa a nearly cylindrical, septate but possibly adventitious ob- 

 ject, like a cast of the interior of the shell of a small Orthoceraa, some two 

 inches in length and fully half an inch in thickness, exposed in the middle 

 of its siphuncle posteriorly. The one presented by Mr. Gunn " which is 

 figured on Plate 31, "has a considerable portion of the ventral side of 

 the body chamber preserved but the lateral margin on both sides is very 

 imperfect. 



" The species seems to differ from the " Orihoceras ( Actinoceras ) 

 Beloitense" of Whitfield,* from the Trenton limestone of Wisconsin, 

 which it resembles in some respects, in its more flattened venter, more 

 concavely arched septa in the ventral region, and in its proportionately 

 larger and apparently nummuloidal siphuncle." 



But, in regard to the siphuncle of T. Rohsoni, it would have been better 

 to say, that its exact shape, size and relative position are not at ^11 clearly 

 shewn in the few specimens yet collected, though it seems to have been 

 marginal and enlarged between the septa. 



CyrTOCERAS (}) CUNEATUM. (N. Sp.) 



Shell widely arcuate, strongly but rather obliquely compressed, very 

 narrow on the periphery or venter, much wider but narrowly rounded 

 on the dorsum, the outline of the transverse section being ovate cuneate, 

 and the lateral diameter to the dorso-ventral about as three to five. 



Septa averaging about six millimetres apart laterally, the sutural lines 

 being shallowly concave on both sides and produced into a narrow pointed 

 saddle on the venter. Siphuncle and test unknown. 



The specimen upon which the foregoing description is based is a cast 

 of the interior of part of the septate portion of the shell. It is evidently 

 not a true Cyrtoceras, but a probably new generic type, which there is 

 not yet sufiicient material to define satisfactorily. 



Trochocebas ijfsiGNE, Whiteaves. 



Plate 41. The only figure. 



Trochoceras insigne, Whiteaves 1898. Ottawa Natiiralist, vol. XII, p. 124. 



Original description. " Shell, or rather cast of the interior of the shell, 

 rather large and attaining to a maximum diameter of fully five inches, 

 dextral and consisting of two slender, closely contiguous volutions that are 

 coiled on very nearly the same plane, and slightly compressed both above 

 and below, so that the outline of a transverse section of the outer volution 

 would be broadly elliptical, with the dorso-ventral diameter a little greater 



' Geology of Wiaoonsin, Vol. IV, p. 226, pi. 8, fig. 1 ; & pi. 10, figa. 9 & 10. 



