BM 



In..-- l! 



II. Sj>. I /7nY/l.> 

 1-1 \ I I I \\XII I II.- 1 .oil . 



T!u> -i>M-ie8 agrees closely with A. rii-limnmleiuu Ulrich, but may be dis- 

 l.y it- mon> distinct and slightly incurved apex, somewhat arched 

 apertun- and -trimmer >urfart> markings. The latter are coarsely lamelliform in the 

 outer third. 



Formation and locaUfy.-Ill<-hm>>iiil croup of tli.> Cincinnati period, Mlddlctowo, Ohlu. 

 L-K. O. Ulrlcb. 



IHUimjx, var. INCPRVA, n. var. 



11 \ri i \ i. nos. Ji-n. 

 MtaMto IIM.I is.;*, 1865, Pal. Fossils, vol. I, p. 251. 



Original Description: "Shell small, depresed conical; apex acute, slightly 

 iin-iii".'- 1. -ituated over the anterior margin; aperture circular; surface finely striated 

 parallel to the l>a--. Width of an average specimen, 8 lines, height 4 lines," 



\ -ingle imperfect specimen, from the Black River group of Minnesota, agrees 

 80 well with Hillings' description and figures of this species, that we hesitate to 

 give it a distinct specific name. The specimen, it is true, is smaller than the New- 

 foundland types and shows besides certain peculiarities that, if they could be proved 

 to be constant, might justify a separation. The apex, for instance, is more incurved 

 in the Minnesota specimen, indeed it curves inward sufficiently to form a complete 

 volution, and the whole dorsal outline is more convex in a side view. Provisionally 

 it may be designated as var. incurva, and it should be added to the list of Black 

 Kiver species mentioned by Billings on page 372 of his 1'al.i ozoic Fossils, vol. i, that 

 are represented by closely allied species in divisions I, K, L and M of the Quebec 

 group in Newfoundland. 



t and lufiility 'I':. .[-- <>r ih. -|M-CI.-- ,ir. fmm ilivisi.in L. Quebec croup. Table Head, 

 .-( .1 l.y I h ii>-ar C;mn<iri Falls, Minnesota, in the Cteno- 



ilunta I* 'i p. 



Collection.-*. 







\I.--||IN\ ^ : \. n. 8p. 



ri.\ 



11 Miiall. nliliijiiely conical. mo<lcrately elevaU'd, aperture rircular. lirin/mital; 

 apex situated almost directly over the anterior margin, apparently small, pointed 

 and slightly incurved; in a side view the posteciur part of the dorsal outline is very 

 gently convex, but in nearing the apex the convexity becomes much stronger. 



