1898] Whiteaves — On some Fossil Cephalopoda 117 



of this beautiful fossil is eighty-eight millimetres, or nearly three 

 inches and a half Its maximum diameter is twenty-six mm. at 

 the larger end and about twenty mm. at the smaller. Its surface 

 markings consist of numerous and densely crowded, but not 

 very regularly arranged, transverse stria?, or minute impressed 

 lines, which are crossed by still more minute longitudinal raised 

 ridges, that are not visible without the aid of a lens. The 

 minuteness of this reticulation gives quite a silky sheen to the 

 exterior of the specimen. Its siphuncle is apparently central 

 or very nearly central. 



A large example of O. tenuistn'atnin, with the test preserved, 

 In the same Museum, from the Trenton limestone at Hull, 

 P.Q., was purchased from a quarryman by Dr. Ami and the 

 writer in May, 1889. It is fully seven inches and a half in 

 length, by about fifteen mm. in diameter at the smaller end, and 

 thirty eight at the larger. Its surface also is very minutely 

 reticulated and has a peculiar silky appearance, 



A fragment not quite two inches in length and about three 

 quarters of an inch in its maximum breadth, collected by Mr. 

 T. C. Weston in 1866 from the Trenton limestone at the Mile 

 End, Montreal, is also probably referable to this species. The 

 surface of this specimen, which although well preserved is not 

 silky in texture, is finely reticulate by densely crowded and very 

 minute transverse stria;, crossed by equally minute and close set 

 longitudinal raised lines and by rather larger and comparatively 

 distant longitudinal ridges, which are from half a millimetre to 

 one mm. and a half apart. It is only these latter that are suffi- 

 ciently large to be visible to the naked eye. 



Orthoceras Westonl (Sp. nov.; 



Shell medium sized, longicone, straight, increasing very 

 gradually in thickness and slightly but perhaps abnormally 

 compressed. Surface marked by very oblique and rather distant 

 flattened annulations, about a millimetre broad and separated by 

 flat spaces from four to five mm. wide. Internal structure not 

 very well shewn in the onlyspecimen collected, butthe siphuncle,as 



