EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 1 03 



is known. It is possible, however, that the coarsely ribbed internal casts 

 may belong to the more finely marked form to which we refer in the 

 following. 



Locality. Presque Isle creek. 



Pterinea radialis Clarke 



Plate 24, figures 31-24 

 Stt also p. 72 



Pterinea radialis Clarke. N. Y. State Mus. Bui. 107. 1907. p. 207 



This is one of a group with an Actinopterialike exterior, but it has the 

 highly developed anterior muscle scar, the umbonal and the lateral teeth of 

 Pterinea. No attempts therefore at correlation with species which have 

 been determined as Actinopteria and Avicula are here called for. The 

 shells have the size and proportions of the foregoing (P. cf. fasciculata) 

 and the following species. The hinge line is but slightly extended pos- 

 teriorly, the anterior wing well marked, convex and sulcatecl ; the crescence 

 line oblique and the valve highly convex in the umbonal region, with abrupt 

 anterior and more gradual posterior slope. The surface sculpture consists 

 of closely crowded subequal rounded riblets, alternation of size being 

 noticeable near the margins. 



Localities. Presque Isle stream, Matagamon lake and elsewhere, Me. 



Pterinea chapmani Clarke 



Plate 25, figure it 



Pterinea chapmani Clarke. N. Y. State Mus. Bui. 107. 1907. p. 203 



A large left valve has the beak almost terminal, a long straight hinge, 

 lateral teeth not visible but umbonal teeth sharply defined ; posterior wing 

 narrow and not extended, anterior wing very small ; anterior slope abrupt, 

 almost vertical ; umbo narrow, elevated, the general surface of the valve 

 broadly convex ; outline oblique. The surface carries faint radial riblets, 

 which are obsolete on the anterior slope. 



The species differs from any of its associates in its obliquity, abrupt 

 anterior slope, abbreviated anterior wing and short posterior extension. 



Locality. Edmunds Hill. 



Pterinea edmundi Clarke 



Plate 24, figures 12-18 



Pterinea edmundi Clarke. N. Y. State Mus. Bui. 107. 1907. p.2O3 



The distinguishing marks of this species are found in its ornament and 

 variable outline. In aspect it approaches very closely the P. radialis 

 from Presque Isle stream but its left valve is sometimes more oblique, 



