CARBONIFEROUS CEPHALOPODS. 347 



measured along the centre of the venter, and only 35 mm. as measured along 

 the side of the whorl. 



These measurements show a more rapid increase than in the whorl of 

 Asympt. capax. The sutures are not only wider apart than in that species, 

 but the form of the whorl also differs. In the figure of As. capax the 

 greatest diameter of the living chamber is above or external to the umbilical 

 shoulder, whereas in this species it is at the umbilical shoulder. The sides 

 converge outwards from these shoulders and are not gibbous as in capax, and 

 in the living chamber, which is evidently very nearly complete on one side, 

 the whorl becomes flatter or more depressed on the abdomen than in capax, 

 and the flaring of the aperture at the umbilical shoulders carries the lateral 

 angles out with great rapidity. The diameter through the widest part of the 

 whorl at the last suture is 68 mm., at a point about half way between this 

 and the aperture about 82 mm., through the wings themselves not less than 

 120 mm., and perhaps a little more in perfect specimens. 



The sutures have a distinct but very shallow broad lobe on the venter, 

 which is irregularly interrupted by the siphon, and there are also shallow 

 lateral lobes. In some specimens the sutures are very likely continuous, as 

 they are in the figure of capax. If the side view of the sutures in the figure 

 of capax is correct, these differ decidedly from those of this species. This 

 shell differs from Asym. Springeri in having less angular umbilical shoulders, 

 a more depressed abdomen, and more convergent sides. In fact, Springeri 

 and capax resemble each other more than either of them resemble this spe- 

 cies.* 



The«comparative length of living chamber can not be given, since the inner 

 whorls were not visible. 



Phacoceras Dumbli, n. s. 



Texas. Coll. Geol. Surv. of Texas. 



Fort Riley, Kansas. Coll. R. Hay. 



Figs. 50, 51, natural size. 



The extraordinarily large size of this shell, its involute form, its com- 

 pressed whorls, and the attenuated character of the outer part of the whorls in 

 proportion to their transverse diameters, combined with the comparatively 

 smooth and ribless shell, makes this species interesting. 



The umbilici are very narrow and small, the involution being almost com- 

 plete. The increase of the vertical diameters by growth is extremely rapid, 

 whereas the transverse diameters have increased very slowly, leaving whorls 

 very much compressed or axe-shaped. The broadest transverse diameters 



*The species has been dedicated to Dr. W. S. Newlori, of Oswego, who found and sent the 



specimen, with some others described in this paper, to the National Museum. 

 30— geol. 



