236 Systematic Paleontology — Middle Devonian 



Description. — Shell of medium size or smaller; ovate-cuneate, sub- 

 nasute behind; proportions of length and height variable but the length 

 usually about one-third greater; basal margin rounded in the middle and 

 at anterior end, straight or slightly constricted toward the posterior end; 

 anterior end abruptly rounded; posterior extremity contracted, cuneate 

 or subnasute, constricted below; cardinal line abruptly declining anterior 

 to the beak, and more gently declining to the posterior. Valves convex 

 below and posteriorly, becoming gibbous above the middle and in the 

 umbonal region ; beaks at about the anterior third, prominent, rising above 

 the hinge-line; umbonal ridge rounded, not strongly defined, with a de- 

 pression or undefined furrow below it, which extends from immediately 

 posterior to the beak to the post-inferior margin. Surface, in well pre- 

 served specimens, marked by fine, regiilar and even, thread-like striae, 

 which frequently become obsolescent in the fun-ow and on the post- 

 cardinal slope; hinge marked by numerous crenulations, which are coarser 

 toward the anterior and posterior extremities. 



A considerable number of well preserved, typical specimens of this 

 species were obtained in the bluish finely arenaceous shales of the Hamil- 

 ton beds in Maryland. This species was also identified by Hall from the 

 Hamilton group of " Pattersons Creek, [W.] Va." (Pal. N". Y., vol. v, 

 pt. i, Lamellibranchiata ii, p. 334) while figures 9 and 14 of plate xlviii 

 are stated to be from the Hamilton group, near Cumberland, Md. This 

 species is readily identified by its constricted and projecting posterior end, 

 its form, and fine, regular, even, thread-like striae which are much 

 fainter or obsolete on the posterior part of the shell. 



E. M. Kindle makes the following statement concerning specimens 

 found in the Onondaga member : 



A Palaeoneilo having apparently most of the essential characters of P. 

 constricta occurs in the same bed with numerous specimens of Chonetes 

 mucronatus. It has the constricted postero-basal margin of that species and 

 fine concentric striae but is rather more gibbous in the umbonal region than 

 ordinary examples of P. constricta. 



Length, 13-17 mm. ; height, 9-11 mm. 



Occurrence. — Eomney Formation, Onondaga Member. Williams 

 Eoad, 3l^ miles southeast of Cumberland. Hamilton Member. East 



