89 



the apex. Chamber of habitation more than one-third the whole length of 

 the shell. Surface with obscure transverse striae. 



The following are the dimensions of the most perfect specimen: — 

 Length on the ventral curve 5^ inches ; diameter of the aperture from 

 the dorsal edge to the most projecting point of the ventral lobe, 21 lines ; 

 lateral diameter on a line drawn across at 5 lines from the dorsal edge and 

 passing through the most projecting points of the lateral lobes, 21 lines ; 

 dorso-ventral diameter at the last septum, 25 lines ; lateral diameter at the 

 same, 29 Unes ; diameter at 27 lines (measured on the dorsal side) from the 

 last septum 10 Hues. The section is, here, circular. Depth of the cham- 

 ber of habitation on the ventral aspect, 31 lines, and on the dorsal, 27 lines. 

 This specimen is broken off at the thirteenth septum ; when perfect it was 

 probably about 7 inches in length. 



Grimsby ; Niagara formation. J. Pettit. 



S. HERDS, n. sp.— Six or seven inches in length and nearly three 

 inches in greatest diameter ; gradually enlarging for about half the length 

 and then tapering. Aperture with the lateral diameter much greater than 

 the dorso-ventral ; trilobed, all three lobes rounded In outline the ventral 

 side is arched to a radius of about four inches, gently curved for the 

 anterior half and more strongly from thence to the apex. The dorsal 

 outline is very gently convex for more than half the length and then con- 

 cave to the apex. Chamber of habitation more than one-third the whole 

 length. Septa three to the inch on the side in the first two inches, more 

 numerous towards the apex. Siphuncle in the median line of the ventral 

 aspect, near the shell but not in contact therewith, two or three lines in 

 diameter. Surface with obscure transverse striae. The following are the 

 dimensions of three specimens : — 



1, — Length on the ventral curve, 7 inches ; dorso-ventral diameter of 

 the aperture from the middle of the dorsal edge to the most pro- 

 jecting point of the ventral lobe, 24 lines ; lateral diameter on a line 

 drawn across at 5i lines from the dorsal edge, and passing through the 

 most projecting points of the lateral lobes, 33 lines ; dorso-ventral diameter 

 at the mid-length, 80 lines ; lateral, 34 lines ; diameter, at 7 inches from 

 the aperture, about 9 lines. 



2. — Length, 5| inches ; dorso-ventral diameter of the aperture about 

 18 lines ; lateral, 27 hues ; dorso-ventral diameter at the mid-length, 28 

 lines ; lateral, 31 lines ; diameter at 5^ inches from the aperture, 11 

 lines ; depth of chamber of habitation on the side, 30 lines. 



3. — This specimen consists of the chamber of habitation (30 lines in 

 depth on the side), and the four last septa. Dorso-ventral diameter of 

 the aperture, 20 lines ; lateral, 29 lines ; dorso-ventral diameter at the 

 last septum, 27 lines ; lateral, 30 lines ; dorso-ventral diameter at the 



