INVERTEBRATES. 391 



J ^g- 3 ^ Shell attaining a large size, length and 



breadth often nearly equal ; very broadly 

 rounded over the dorsum ; umbilicus deep, 

 less than half as wide as the transverse di- 

 ameter of the outer whorl; volutions more 

 than three times as wide transversely as 

 the diameter from the dorsal to the ventral 

 side, subangular around the margin of the 



Goniatites globulosus. ' CJ ° 



outline of the typical speci- umbilicus. Aperture lunate, breadth about 



men, natural size, to show the •"- ' 



Kffi7tK?rtl three and a half times the dorso-ventral 

 diameter. Surface of internal casts sometimes slightly con- 

 stricted at intervals, as if from an occasional thickening of the 

 inner lip. Septa moderately distant; dorsal lobe nearly as 

 wide as long, and deeply divided into two slightly diverging, 

 simple, lanceolate branches; dorsal saddle linguiform, being 

 regularly rounded at the end, and a little narrower than the 

 dorsal lobe, but equaling it in length, and slightly contracted 

 in the middle; superior lateral lobe as long as the dorsal sad- 

 dle, but narrower, and pointed at the extremity ; lateral saddle 

 a little broader than the dorsal saddle, which it resembles in 

 other respects, excepting in being shorter on the ventral side ; 

 inferior lateral lobe very short, but with a pointed apex — not 

 visible when the umbilicus is filled. Surface unknown. Length 

 or greatest diameter., of the typical specimen, 1.18 inches; 

 height, 1 inch; breadth near the aperture, about 1.18 inches. 



Prof. Cox has figured in the Kentucky Report, vol. iii, pi. x, fig. 1, a shell 

 which seems to be related to this, but from the measurements given by 

 him it is manifest that the form he has figured is more compressed, and has 

 a proportionally smaller umbilicus, while his diagram of a septum shows a 

 more deeply divided dorsal lobe, with less spreading divisions. He also repre- 

 sents the sinus of the dorsal lobe as being pointed instead of obscurely bifid, as 

 in our species, and the dorsal saddle pointed instead of rounded at the extremity. 

 Our shell likewise differs in having a proportionally smaller superior lateral 

 lobe.* 



* In making comparisons with Prof. Cox's description and diagram, it is necessary, 

 in order to understand him clearly, that the reader should bear in mind that he has 



