1888.] 473 [Newell. 



City. These are compressed laterally and though the outlines of 

 the apertures are very dimly shown, yet the characteristic com- 

 pressed T-shaped opening above described can be discerned. In 

 outline, the living chamber agrees with G. Wabashensis in de- 

 creasing in size from the base upward. These specimens have 

 several closed chambers attached. They show that in general shape 

 the shell was nearly straight ; the dorsal and ventral sides being 

 both convex, the dorsal slightly more rounding than the ventral. 

 The increase in size from the smallest chamber upwards is quite 

 rapid. On the best preserved specimen, figured above, the dorsi- 

 ventral diameter of the lowest suture, the sixth from the base of 

 the living chamber, is 45 mm. ; the base of the living chamber is 

 73 mm. and the distance between these two diameters is 50 mm. 

 The thickness of the closed chambers averages a little less than 

 9 mm. The greatest vertical height of the living chamber is along 

 the central vertical axis, which equals in length the dorsi- ventral 

 diameter of the base. 



GOMPHOCERAS LINEARIS n. Sp. 



Compare Gomphoceras (Phragmoceras) labiatum Whitf., Geol. Wise, iv, 

 p. 302, pi. 20, figs. 1 and 2. 



Shell of medium size, arcuate, increasing rapidly in diameter 

 from the apex to the apertures ; the ventral side is slightly con- 

 cave, dorsal strongly convex ; transverse section narrowly ellipti- 

 cal, ventral side angular, dorsal narrowly rounding. Apex unknown. 



The living chamber is large, rhomboidal in lateral outline. Its 

 bulk is fully two to three times that of all the closed chambers to- 

 gether. The length is one-fourth less than the clorsi-ventral diam- 

 eter of the last septum. It increases in length and breadth to the 

 region of the apertures where the side flaps turn abruptly toward 

 each other making a long flat top parallel to the base of the cham- 

 ber. The sides of the aperture approach so closely that they 

 leave the slit connecting the ventral and dorsal regions scarcely a 

 millimetre in width. The length of this linear slit (from which the 

 species is named) is one-fourth greater than the clorsi-ventral diam- 

 eter of the base of the living chamber, and also greater than the 

 entire length of the shell, being proportionally longer than that in 

 any species yet described. The ventral opening is elliptical and 

 prolonged forward in a tube-like projection, but its entire length is 

 not shown, the cast being broken. The dorsal opening is in general 



