26 



to one line from each other, the intervening spaces flat and with from three 

 to seven finer strias just visible to the naked eje ; in others the interven- 

 ing spaces are concave. In many the principal striae become coarser 

 and closer together, until the whole surface is covered with strong angular 

 bifurcating ridges from one-fourth of a line to half a hne in width. In 

 very well preserved specimens of these latter, the coarse ridges are seen 

 to be themselves ornamented with the fine longitudinal striae. In all cases 

 the whole surface, when perfectly preserved, is beautifully cancellated by 

 minute crowded concentric strias. 



It would require a great many figures to represent all the forms of this 

 species. The two given may be regarded as central and typical. The 

 • departures from these two consist principally in the contraction or exten- 



sion of the cardinal angles ; the greater projection of the front margin? 

 which is sometimes narrowly instead of broadly rounded. Fig. 13 above, 

 is from the Corniferous limestones, Ontario, and represents a form with 

 strong radiating striae. Fig. 4, pi. 2, is from the Gaspd limestones, the 

 larger striae distant with flat intervening spaces of fine, closely crowded^ 

 striae. 



The deltidium in one specimen is shghtly convex on each side of the 

 central ridge. In some a portion of the sides of the shell ii bent nearly 

 at a right angle towards the dorsal aspect. 



In the publications of the Survey, this species has been heretofore 

 referred to, S. incequistriata^ Conrad. Prof. Hall has described and 

 figured it in the 4:th vol. Pal., Y., under the name of S. inequiradiata. 

 As that arrangement will most probably be followed, it is best for the 

 sake of uniformity to adopt it. Although from Conrad's figure and 

 description it is not certain that this is the form intended by him. 



Locality and Form^^tioyi, — Indian Cove, Gaspe Bay. No. 8. Also 

 in the Oriskany sandstone and Corniferous limestone, Ontario. Occurs 

 in N. Y. in Schoharie grit and Corniferous limestone. 



Collectors.— ^iv W. E. Logan, R. Bell. 



Strophomena varistriata. (Conrad). 



PI. 2, fig. 3. 



Strophomena varistriata. (Conrad.) Jour Acad. Nat. Sci. Phi., vol. VIII, p. 255, plate 



14, fig. 6. 



Strophodbnta varistriata. (Hall.) Pal., N. Y., vol. III. 



Description, — The form of this species is exactly like that oi S. inequi- 

 radiata^ the only difference being that the shells are smaller. The sur- 

 face characters are also the same. None of the specimens collected at 

 Gasp^ exceed an inch in width on the hinge line- Some of them have the 



