EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 187 



while in the other species the outhne is more elongate-semielhptical, the 

 lateral and anterior margins form a continuous easy curvature and the 

 cardinal angles are more acutely rounded. These differences produce a 

 notable distinction in the general habit of the species. The Grande Greve 

 limestone shells palpably express the characters of S. i n e q u i r a d i a t a 

 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 

 fasciculation gradually becomes lost or passes into an irregularly unequal 

 striation. The corrugations are restricted to the fasciculate area. 



Strop heodonta 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. i n e q u i r a d i a t a 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 ofS. patersoni. 



Dimensions. Fully developed examples attain a length of 25 mm and 

 a width on the hinge of 40 mm. 



Localities. Grande Greve, Indian Cove, Little Gaspe ; near the top 

 of the limestone. 



Stropheodonta crebristriata Conrad (Hall) protype simplex nov. 



Plate 35, figure 14 



See Hall. Palaeontology of New York. 1867. 4:86, pi. 11, fig. 12, 13, 18-21 



On comparing with the hypotypes of this species illustrated in the 

 work cited, a few shells from Grande Greve, we observe that the young 

 condition of S. crebristriata (a Schoharie grit species in New York) 

 represented by the original of plate 11, figure 13 \op. eiL] corresponds 

 remarkably in size contour and surface with these. The shells in hand are 

 quite regularly convex having the greatest width along the hinge, a semi- 

 elliptical marginal outline and the surface bears 8 to 10 sharp angular but 

 not elevated plications, which increase in number by implantation so that 

 the margin bears at least four times as many plications as the beak. In 

 S. crebristriata, as referred to, there are about the same number of 

 plications though they are individually less prominent and their duplication 

 begins somewhat earlier. This specimen shows a fine interlineation which 

 we observe only at the margin of the Gaspe shell. 



We construe this shell as a simple and early expression of 



