271 

 Stropheodonta (Brachyprion) Niagarensis 1 ■ 



(Winchell ifc Marcy.) 



Cfr. Strophoviena niagarensis, Winchell & Marcy. I860. Mem. Boston Soc. Nat. Hist., 



vol. I, p. i)2, pi. 2, fis. 9. 



Strophodonta profunda, fpars) Hall. 1867. Twentieth Ann, Rep. Reg. Univ. St. N. 



York, p. 369. pi. 13 (4), figs . 3 and 4. 



Two very immature, detached valves of a strophomenoid shell, that cor- 

 respond very well in all but size, with the descriptions and figures of the 

 exterior of this species. The more perfect of the two, a small ventral 

 valve, is moderately convex, wider than long, and its cardinal angles are 

 produced. Its surface markings consist of fine radiating raised lines, with 

 from two to six still smaller ones between each pair of the larger ones. 

 The characters of the interior are not shewn in either. Both of them are 

 from loose pieces at or near the mouth of the river. 



One good sized and fairly well preserved specimen, collected at an ex- 

 posure ten miles above the mouth of the river, has been kindly compared 

 with typical western specimens of S. Niagareixsis, by Mr. C. Schuchert. 

 These western shells, Mr. Schuchert thinks, are " more convex, and their 

 larger strise more prominent, causing the intermediate areas with the 

 finer strise to be more depressed," but these may be only local peculia- 

 rities. At the same locality three other Strophomenoids were collected, 

 which may prove to be varieties of S. Niagarensis, but which do not 

 shew the characters of the hinge area, or of the interior of either valve. 

 One is a small ventral, with very fine and equal radiating strise. The 

 other two are medium sized detached valves that are moderately convex, 

 or tumid, gibbous and geniculate, at about the midlength, wider than 

 long, with the cardinal angles slightly produced, and the front margin 

 nasute. Their surface markings consist of minute, fasciculate, radiating 

 raised lines, with minute punctures between them. According to Mr. 

 Schuchert, iS". Niagarensis is " closely related to StrophoTnena imbrex, 

 Pander, variety, as identified by Lindstrom f rom the Silurian of Gotland," 

 and E. Billings has recognized and recorded S. imbrex as occurring in the 

 Hudson River formation at Cape Robert, Anticosti. 



A concave dorsal valve from an exposure thirty-one miles above the 

 mouth of the river, may also be referable to S. Niagarensis, though it 

 shews only the general shape, and the surface markings of the exterior, 

 but neither the hinge area, dentition, nor any of the characters of the 

 interior. 



Lept^ena rhomboidalis, Wilckens (Sp). 



Three very small but characteristic specimens in a small loose block of 

 limestone, picked up at or near the mouth of the river. 



