EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 2~] 



anterior wing is small, the beak subterminal and anterior slope quite direct. 

 Concentric growth lines only are visible on the surface. This is a species 

 suggestive of several which have been described from late Siluric and early 

 Devonic beds, e. g., P. retroflexa Wahl. (Upper Ludlow) and spe- 

 cially P. pseudolaevis Oehlert from the lower Coblentzian, from which 

 it seems to differ in form only in its smaller anterior wing. 

 Horizon. Nos. 9, 13. 



Pterinea fasciculata Goldfuss var. occidentalis Clarke 



Plate 4, figures 1-7 



Pterinea fasciculata Goldfuss var. occidentalis Clarke. N. Y. State Mus. 



Bui. 107. 1907. p. 205 (figures of P. cf. occidentalis fasciculata on p. 204) 

 See Pterinea fasciculata Goldfuss. Petrefacta Germaniae, 2:137, pi. 129, fig. 5, 



and Freeh. Devon. Aviculiden Deutschlands. 1891. p. 84, pi. 8, fig. 1; pi. 9, fig. 1-3 



This extremely common shell is essentially a miniature of P. fasci- 

 culata Goldfuss. Though reduced in all its proportions and in the 

 strength of its ornament yet it expresses excellently the characters of the 

 German species. The valves are both convex, the left notably and the right 

 but slightly. The left valve has the body well elevated above the posterior 

 wing-. This wing is sometimes more incurved at the margin and more 

 extended at the point than in the figured German specimens but these 

 features are variable in the Dalhousie shells. The body of the shell or 

 direction of the crescence line is commonly more oblique than in European 

 specimens but this is an expression due in some measure to mode of 

 preservation, for examples occur here quite as erect as those referred to. 

 The breadth of the byssal groove and emargination on the valve are also 

 notable ; together with the relative development of the anterior ear they 

 are in full agreement with P. fasciculata. The surface of this valve 

 is marked by coarsely fasciculated radial striae. The major ribs do not 

 exceed five or six but these are widely separated on the body of the shell, 

 the interspaces occupied by radii of lower order. 



On the posterior slope the striae are of uniform size and are visible on 

 the wing. On the anterior wing there are two or three coarse riblets but 

 the byssal sinus is deep and without radii. Crossing these elevated radial 

 lines are fine crowded and elevated concentric lines giving all the surface 

 except the byssal sinus a reticulate ornament. 



The right valve is much less convex than the left, the anterior wing 

 relatively large, the byssal sinus deep, the body of the shell depressed. The 

 surface bears a few simple filiform radial lines along the body of the shell 

 and others are visible on the posterior wing at the hinge. No concentric 

 lines are evident. 



Horizon. No. 1 1. 



