OASTBOPOI'A 1011 



Plelhoaptra ttrlU J 



PLKTHO-IIKV -TRIATA, *. tp. (Ulrich.) 



PLATE I.XX. ttO. T. 



Shell turblnate, apical angle at leant 86, hlghl nearly 2Z mm. , width about 19 mm.; volution* at 

 leant four, probably flve, convex below, nearly vertical In the middle third, concave above the band, hori- 

 zontal between the upper carlna and the suture ; band supra-median on the lut, Infra-median on the 

 whorls of tb>> spire, decidedly concave, with thick and prominent maiylns ; lln-s of growth rather regu- 

 lar, strong and heavy, rounded, wave-like. tlve or six on the last whorl In 4 mm. ; on the upper side they 

 curve strongly backward, beneath the hand they are almost vertical aavlng a very short n-tral curve 

 above: lunula- obscure; aperture rounded-pentagonal, outer Up with a broad but very shallow notch, 

 rolumellar Up straight, ohtusely angular below, reflexed, completely covering the minute umbilicus. 



This well-marked specie* cannot be confounded with any other shell known to us. The surface 

 markings are highly characteristic. 



Fonwitiem and totality. Richmond group, Hanover, Butler county, Ohio. . 



CoUtcUo*.-E. O. Ulrich. 



Genus SEELYA, n. gen. (Ulrich.)* 



PUurotamarui. ID part, of MUK and WOKTIIEN, and WIIITKIKLD. 



For generic diagnosis see page 958. For figures of typical species see page 1009. 



The species which we propose to arrange under this generic title agree closely 

 with Plethospira in all respects excepting that they have a narrower band and a 

 spirally furrowed surface sculpture. As the group is easily recognized, a natural 

 one, and ranges from the Calciferous to the top of the Niagara, we think that it 

 should be distinguished by a name of its own. Whether the group is to be viewed 

 as a genus or as a subgenus is of little consequence now. Our knowledge of Paleozoic 

 Gastropoda is yet far from that point when we may decide such questions with 

 anything like confidence in the stability of the result 



In the Calciferous of the Champlain valley we have two species of this genus, 

 the type, S. ventricosa Ulrich, and Pleurotonmria difficilis Whitfield. These possibly 

 are not distinct, but if W bitfield's figures of his species are correct, and we have no 

 reason to doubt it, then it is clearly another form, having a lower spire, more 

 numerous revolving furrows, and a shoulder-like angalation near the suture that is 

 wanting in S. lentricnsa. An imperfect specimen in the U. S. National Museum, 

 which seems to belong to Whitfield's species, differs further in having a larger 

 umbilical perforation. 



Judging solely by the illustration given by Billings in Paleozoic Fossils, vol. i, 

 p. 187, fig. 171, of his Murrhisonia catsandra, we would say that the species was 



Th rnoU named to booor of Prof H M. Seely. of Mlddlebury Collate, who, beoaoM of bU raluable work on the 

 < alclferoui-Cbuy fauna and roelra of the Champlain rally. In connection with Prof. Bralnrrd. hu fully earned the com- 

 pliment- One of the author. l aUo Indebted personally in Prof. 8ly fur numerous ipecliuenn. among them the type of 

 tbe praaent (aaa. from Fort CaMlo and other local lilei In the Cbamplaln valley. Tbwe bare been of much aMUtaoo* la 

 our work. Some p&leootolocteu probably will eonUnd that the namo theuld bare been written Sttltfa, but tbe aborver 

 form M*a MMMd w prefiratile tbat we concluded to rlak their crltl 



