698 Systematic Paleontology — Upper Devonian 



and concave on the -umbilical side. The enlargement of the volutions is 

 very gradual; the base of the air chamber, at the end of about the fourth 

 volution, measures a little more than thirty mm. The inner volutions 

 are not in a condition to be measured. The chamber of habitation, known 

 only at its commencement, is continued in the same proportions as the 

 preceding chambered portion of the shell. Aperture unknown. Air 

 chambers numerous; the width of the volution is equal to about three 

 chambers in their greatest depth, and nearly twice as many at the umbili- 

 cal margin. Septa thin, somewhat regular in their arrangement; the 

 margins moderately thickened, and slightly imbricating; distant from 

 each other, at their origin on the umbilical side, from three to five mm. 

 in the last fourth of the outer volution, the last two being closer than any 

 of the preceding. From the umbilical side the septa proceed in a gener- 

 ally transverse direction, making several abrupt curves, the posterior ones 

 of which are angular, and describing four saddles, of gradually increasing 

 height and dimensions, and three shallow, angidar lobes on the inner 

 half of the width of the volution ; on the outer half of the volution there 

 are deeper and more abrupt curves; and leaving the base of an angular 

 lobe at about the center, the septa describe a wider semielliptical saddle, 

 a deeper elongate subangular lobe, and a still more elongate and more 

 elevated saddle, which has its apex near the periphery. On the outside 

 of this there is a narrow lobe, and an abrupt turn of the septum to the 

 periphery, upon which its course has not been observed. This arrange- 

 ment gives six lobes on the lateral face of the volution, each one of which 

 has an increasing depth from the umbilical margin. There are likewise 

 six saddles, each successive one of which is higher and wider than the 

 preceding, except the last which is much higher, but not quite so wide as 

 the one preceding it. Suture lines narrow, moderately impressed upon 

 the vast, and more strongly marked at and near the extremities of the 

 lobes and saddles. Siphuncle unknown. Test entirely unknown. The 

 surface markings cannot be satisfactorily determined on the cast of the 

 interior or upon the weathered impression of the exterior, which are the 

 only portions preserved. The cast of the interior is marked by nodulose 

 annulations, which are nearly continuous on the inner half of the volution. 



