177 



diameter at the aperture in the two species is the same very nearly, but 

 at three inches therefrom it is 14 lines in one specimen, and a little less 

 than 12 in Prof. Hall's figures. 



Locality and Formation. Drummond Island ; Hudson River formation. 



Collector. A. Murray. 



CYRTOCERAS JUVENALIS. (N. sp.) 



Description. Short, ventricose, rather strongly curved. Section nearly 

 circular, near the aperture the dorso-ventral diameter a little longer 

 than the lateral ; at the last septum circular, or very nearly so ; the 

 ventral side is slightly more narrowly rounded than the dorsal. Septa 

 about four in three lines where the diameter is seven lines. 



Surface obscurely reticulated. The transverse striae are minute, not 

 sharp, accompanied by a few obscure undulations of growth, and make a 

 backward bend on the median line of the ventral aspect. The longitudinal 

 lines are straight, three or four in the width of one line, not strongly 

 developed, but still distinctly visible. 



The specimen is 21 lines in length along the ventral curve, which has 

 a radius of 10 lines. Dorso-ventral diameter at the larger extremity 

 (supposed to be very near the aperture) 7f lines, lateral 7i lines ; at 6 

 lines nearer the apex (supposed place of last septum) the dorso-ventral 

 diameter is 8| lines, lateral nearly 9 lines ; from this point the shell 

 tapers to a diameter of 5J lines in the length of about 1 inch, the section 

 still remaining circular, or nearly so. 



Locality and Formation. Montreal ; Trenton limestone. 



Collector. McLachlin. 



CYRTOCERAS ORESTES. (N. sp.) 



Description. Shell strongly curved ; in the first four and a-half inches 

 of its length (measured on the outside) forming nearly a half circle with 

 a radius of twenty-one lines ; the larger extremity with a more gentle 

 curve than the smaller. Dorso-ventral diameter at the last septum four- 

 teen lines ; lateral diameter at the same place twelve lines ; depth of cham- 

 ber of habitation fourteen lines. Where the dorso-ventral diameter is nine 

 lines, the septa are nearly two lines distant on the ventral margin. Siph- 

 uncle about one line in diameter, and with its centre distant about one 

 line from the ventral margin. 



Locality and Formation. Tenth lot of the first concession of the 

 Township of West Flamborough. Niagara limestone ; Middle Silurian. 



Collector R. Bell. 



