EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA I 55 



the margin. Concentric sublamellose lines at distant intervals. On the 

 wing radial lines are obscure but concentric lines sharp and crowded. 



Dimensions. The typical specimen has a length of 47 mm ; hight of 

 42 mm. 



Locality. Perce Rock. 



Species najne. Jumeau, Recollet colaborer with Chrestien LeClercq at 

 Perce. 



Aviculopecten ? incrassatus nov. 



Plate 18, figure i 



Shell large, outline obliquely subelliptical. Posterior wing short. 

 Surface with coarse and heavy radial ribs of unequal size separated by rela- 

 tively narrow rounded grooves. Inequality in the size of the ribs is notice- 

 able in the umbonal region and new ribs are added by division of the large 

 ones. All are crossed by a concentric ornament of fine compressed lines 

 with occasional deep concentric growth furrows. This type of ornamenta- 

 tion is an extreme condition of that sometimes expressed by Pterin- 

 o p e c t e n p r o t e u s. The original specimen has a hight of 50 mm and 

 a probable length of 70 mm. 



Locality. Grande Greve. 



Actinopteria communis (Hall) 



Plate ly, figures 8-12 



Avicula communis Hall. Palaeontology of New York. 1859. 3: 286, pi. 52, 



fig- 1-7 ; Pl- 53, fig- T, 4, 6 

 Actinopteria communis Clarke. N. Y. State Mus. Mem. 3. 1900. p. 34, 

 pl. 4, fig. I, 2 



The Grande Greve material affords an occasional specimen of small 

 size in which the characters of this species are fully developed. In the 

 Perce Rock the species is represented by much larger shells of greater 

 obliquity and these may be regarded as a mutation of the specific form. 



Actinopteria communis was described from the Helderber- 

 gian fauna but also occurs in the Oriskany of Becraft mountain. The 

 ornament of the wing is strongly lamellar concentrically and in sharp con- 

 trast to the rest of the shell. As a whole it is clear that the ornament of 

 this species stands in a primitive relation to the progressed ornament of 

 A. communis and that the simple type of expression in this ornament 

 at adulthood is an indication of arrest of development. 



Localities. Along the shores at Grande Greve and at Percd 



