COAL-MEASUEE AND PERMO-CAEBONIFEROUS FOSSILS. 279 

 Genus GONIATITES De Haan. 



GONIATITES KiNGII D. Sp. 



Plate VI, figs. 9-14. 



Shell rather below the medium size, subglobose, the length and breadth 

 being about as three to two; composed of from four to six volutions, which 

 are broadly rounded over the dorsum and subangular at the margin of the 

 broad open umbilicus, into which the sides slope abruptly, forming an angle 

 of about forty-five degrees to the axis of the shell. Each volution em- 

 braces the preceding one to near the lateral angle, leaving a very narrow 

 surface exposed within the umbilicus. Extreme width of the volution equal 

 to three times the length, measured from the ventral to the dorsal surface, 

 at the center of the volution. 



Surface of the shell and umbilicus marked by fine, subequal, trans- 

 verse lines of growth, often becoming crowded, and forming incipient un- 

 dulations on the back of the shell. Surface of the internal casts sometimes 

 marked by transverse constrictions, caused by the thickening of the inner 

 surface of the lip at stated periods of growth, as if for the purpose of strength- 

 ening its substance. Two of these constrictions occur in the space of one 

 volution, bringing them on opposite sides of the cast Septa rather closely 

 arranged and deeply lobed. The dorsal lobe is longer than wide, and deeply 

 divided, forming two long, slender, lanceolate branches, with a shorter, trun- 

 cated, central projection; dorsal saddle broadly conical, rounded above, and 

 slightly inclined toward the dorsal lobe; lateral lobes as long as the dorsal 

 saddle, obconical, pointed at the lower extremity; lateral saddles broader 

 and shorter than the dorsal saddles. 



The shell is somewhat remarkable for the great extent of the outer 

 chamber, appearing from fractured individuals to consist of two complete 

 volutions, and in some cases even more. It does not appear to attain a very 

 large size ; the largest fragment observed indicating a specimen of not more 

 than two inches in diameter. 



The species is of the type of G. sphericus Sow., but is less globose and 

 the umbilicus much larger. There are several American species of the type 

 known, as G. NoJmensis Cox and G. globulus and G. lowensis M. & W. from 



