64 NE W YORK STATE MUSEUM 



Poleumita crenulata Whiteaves (sp.) 



Plate 9, fig. q, 11, 16-24 



Straparollus crenulatus Whiteaves, Paleozoic Fossils. 1884. v. 3, pt 2, 



p. 21, pi. 3, fig. 8a, b 

 Polytropis crenulatus Whiteaves, Paleozoic Fossils. 1895. v. 3, pt 2, p. 91 



Dr Whiteaves states that he had but two specimens of this species in 



the collections from the Guelph at Durham, and from these he drew his 



description. In the Arey collection are upwards of 30 specimens, which 



show that the species is specially characteristic of this eastern development 



of the Guelph. About half as many have been collected in the lower 



bed at Shelby but none at all obtained from the upper Guelph horizon, 



where P. scamnata was found inconsiderable number. This abundant 



material does not qualify the very clear and full description of the species 



given by Whiteaves, which we here reproduce. Our larger series, however, 



shows that wider variations exist in the elevation of the spire and surface 



sculpture, as the few specimens from Durham would indicate. 



Shell turbinate, compressed vertically, hight one third less than the 

 maximum breadth ; whorls three to four [5] ; spire short, about one third 

 the entire hight, somewhat conical, its volutions being obliquely rounded ; 

 suture excavated ; body whorl compressed vertically both above and below, 

 ventricose and inflated in the middle ; umbilicus about one third the diam- 

 eter of the base, very deep and exposing all the inner whorls up to the apex ; 

 mouth nearly circular but narrower above and very slightly emarginated or 

 indented by the penultimate whorl ; outer lip apparently thin and simple, 

 convex above and obliquely convex below. Surface marked by a few nar- 

 row and not very prominent spiral ridges which are crossed obliquely by 

 numerous flexuous crenulated raised ridges or lamellae. On the outer half 

 of the body whorl there are about seven or eight of these spiral ridges, four 

 above and either three or four below the middle. The upper ones, one of 

 which is placed very close to the periphery, are distant and rather clearly 

 defined, but the lower ones are close together and extremely indistinct. 

 These latter two are exclusively confined to the outer portion of the base, 

 and disappear altogether before reaching the umbilical margin. The crenu- 

 lated raised lines, however, which cross the whorls obliquely, are as strongly 

 marked in and around the umbilicus as they are on the central and upper 

 portions of the body whorl, and they are much more numerous as well as 

 more closely disposed than the spiral ridges. 



