270 NEW YORK STATE MUSEUM 



rugations, S. varistriata is not only smaller but more nearly 

 square in outline with nearly rectangular cardinal angles ( S. recti- 

 lateralis being one of Conrad's synonyms) while in the other 

 species the outline is more elongate, semielliptical, the lateral and 

 anterior margins form a continuous easy curvature and the car- 

 dinal angles are more acutely rounded. These differences pro- 

 duce a notable distinction in the general habit of the species. The 

 Grande Greve limestone shells palpably express the characters of 

 S. inequiradiata and S. patersoni; but in so far as 

 differences in these two are concerned it is to be noted that in 

 the former the fasciculation is best expressed over the middle parts 

 of the shells, but in later growth about the periphery this fascicula- 

 tion gradually becomes lost or passes into an irregularly unequal 

 striation. The corrugations are restricted to the fasciculate area. 



S. patersoni, holding its fasciculate character throughout 

 growth, is in an arrested condition with reference to this species. 

 The Grande Greve shells seem rarely to pass the stage in which 

 the fasciculation of the striae is obscured as in S. inequi- 

 radiata but neither do they always present the corrugations 

 of S. patersoni. These corrugations are usually present, 

 sometimes very strongly developed, again obscure, but they may 

 be altogether absent leaving the simply fasciculate exterior so 

 prevalent in the Strophomenidae throughout their history. In view 

 of these facts we prefer to designate the Grande Greve shells as 

 a variation or protype of S. patersoni. 



Dimensions. Fully developed examples attain a length of 25 mm 

 and a width on the hinge of 40 mm. 



Lower Devonic. Grande Greve, Indian Cove and Little Gaspe, 

 P. Q. 



Stropheodonta patersoni Hall protype bonamica nov. 



We have noted the difference in the Grande Greve form 

 of S. patersoni and the typical expression of the 

 species in the Onondaga limestone of New York. In the shell 

 before us we have a quite different expression of this type, rare 

 in American waters. The type itself, we may briefly reiterate, is 

 expressed in the highly convex form, the strong fasciculation of 

 the striae and the corrugation of the umbonal portion of the valves. 

 We are here presented by a relatively small and quite narrow shell 

 with a short, straight hinge, prominent cardinal extremities, highly 

 convex or gibbous curvature (ventral valve) and greatly produced 



