OASTKnl'iiJ.A l'N'7 



Ullhnplr cnervxk.) 



. lunuhi' of the band are distinct, strongly curved, and croHed by a varying nuniN-r of delicate 

 Suture linear ami inconspicuous -v-|>t between the last two whorls of old shell*. The 

 last volution usually descends more rapidly than the preceding whorls. 



In cast* of th- interior, the condition In which this fossil usually occurs, the suture, for obvious 

 reasons, Is deeper than In th>- shell itself. th>- periphery of the whorls oftener rounded than Hat or concave, 

 AIK I tin- -urface markings restricted to more or lens obscure Impressions of the varlces of growth. Even 

 '. the eiterlor In the dolomltlc limestone In which the species occurs so abundantly In Wiscon- 

 sin and Minnesota, only In rare Instances preserve any recognizable traces of the delicately cancellated 

 surface sculpture. Hut we have nev to detect It whenever the grain of the matrix was One 



enough. That the surface In these specimens was originally cancellated, as shown in figure 6 on plate 

 1. \ \. I* further established by two specimens collected by on- of tin- authors In tho One-grained upper 

 Hi-nil., r of tin- Stoni-s Uiv-r group at Dlxon, Illinois. These specimens preserve not only portions of the 

 outer layer of the shell with its beautiful markings, but here and there retain Irrldescent patches of tin- 

 nacrous Inner layer which, since it baa been observed In so many different forms, probably pertained to all 

 of the PlntntomarUdae. 



We are In doubt as to the occurrence of this species In the Black River shales of Minnesota. The 

 small casts usually referred here by collectors belong chiefly to our C. contra. Some of the others may 

 represent C. tttamtco, but we have not seen any of which we would like to say positively that It does. 

 Nor have we seen a specimen (neither the CUtambonlteH, Fuslsplraor Mac! urea bed of th- Trenton group. 

 If It occurs at any of these horizon* in Minnesota, It must be very rare. Casts of a species of CioMrtMpt'ra 

 occur In Hi- Lorraine and Richmond groups of the Cincinnati region. They have always been regarded as 

 belonging to C. gubroiuca, but < 'erous specimen of CUithrotpira that we bare seen from that 



region has proved to belong to our C. ronica. Though It must be admitted that the occurrence of C 

 ftttamtca In the Cincinnati rocks requires verification, we are fully prepared to believe that many of the 

 Interior casts found there are really of that species, and until we know better they should be so regarded. 



formation and locality. Stones River group, Minneapolis, St. Paul, Cannon Falls, and other 

 localities in Minnesota; Belolt, Janesvllle, and other localities In Wisconsin; Dlxon, Kockton, and Jo 

 Daviefts and Calhoun counties In Illinois; High Bridge, Kentucky; Lebanon and other points In Tennessee. 



n the Black River group at several of the foregoing localities. In Canada and New York It occurs 

 In the Black River and Trenton groups, and probably also lii the Hudson River group. In Ohio, Indiana 

 and Kt -mucky, casts supposed to belong to this species occur at many localities in both the Lorraine and 

 Richmond Croups. 



CWieetfMts. Geological and Natural History Survey of Minnesota; E. O. Dlrich; W. H. Scofield. 

 Mtatum IltyitUr, No. 5037. 



1HROSPIRA CONVEXA, H, 8p. 

 PLATE LXIX. PIG 51? 



Casts of the interior, the only condition In which we have observed this rare species, agree MTV 

 closely with f. wboonica In all respects save In the contour of the upper side of the volutions. Tin-. 



1 1 of u-lng n.-arly flat (i. t. gently convex above nd slightly concave below) in the space between the 

 suture and the upper margin of tin- peripheral band, Is rather strongly convex. The elevation of the 

 band produces a narrow concavity immediately above It. out this d.-s not greatly effect the general 

 roundness of the whorls. Tr - .unded than angular: In C. utamka the opposite Is the case. 



-peclmen figured on plate LXIX has all the appearances of being fully grown. If t! then 



C. ooatww is a smaller shell than C. mtamr<i. Th- same specimen preserves traces of the surface sculp- 

 ture. This Is of a coarser pattern than that of C. mtamfca, there I four or five of the Iran 

 lines in 2 mm. Instead of sevens > 



Formation and locality. Stoaes River group, Calhoi. Illinois. 



OoUettion.-E. O. Ulrlch. 



