652 Systematic Paleontology — Upper Devonian 



truncated i)ostei'iorl_y by a strong ridge or clavicle. Pallial line parallel 

 to and near the basal margin, appearing as a shallow groove, recurving neai- 

 the postbasal extremity and terminating in a broad, muscular impression, 

 the anterior margin of which is near the center of the length of the shell. 

 A specimen of medium size is 54 mm. in length and 20 mm. in 

 height. This species is ver\' closely allied to G. perangulala of the 

 Schoharie grit, and it is possible that they are identical. In the specimen 

 fig. 3 of plate xl, the hinge-line is shorter than in specimens of G. per- 

 angulata, but the comparative length of the hinge-line appears to be 

 variable in the tM'o species." Hall, 1885. 



This species is distinguished from others in the fauna by its small size, 

 its oblique truncation posteriorly, and very angiilar posterior umbonal 

 slope. The individuals observed in Maryland seem uniforaily smaller 

 than those figured by Hall from New York, and do not show a distinct 

 sulcus in front of umbonal slope. 



Occurrence. — Jennings Formation, Parkhead Member. Williams 

 Eoad, on Polish Mountain, 1600 common; 'ZVo miles above mouth of 

 Sideling Hill Creek. 



Collection. — Maryland Geological Survey. 



Goniopijora glauca Hall 

 Plate LXV, Fig. 7 



Sanguinolites glaucvs Hall, 1840, Prelim. Notice Lammellibr., Pt. il, p. 38. 

 Goniophora glaucus Hall, 1885, Pal. of N. Y., vol. v, pt. i, sec. ii, p. 299, pi. 

 xliii, fig. 16; pi. xliv, figs. 10-17. 



Description. — " Shell large, trapezoidal; length once and a half greater 

 than the height; basal margin gently curved, sometimes scarcely sinuate 

 anterior to the middle; posterior margin obliquely truncate; cardinal 

 line nearly straight or slightly oblique; anterior end declining from the 

 beaks and abruptly rounded below. Valves moderately convex below, some- 

 times becoming gibbous on the umbonal region. Beaks subanterior, small 

 and closely appressed ; umbo prominent; umbonal ridge more or less 

 strongly defined and distinctly angular, extending to the postbasal extrem- 

 ity'. Test of moderate thickness, marked by regular, concentric, thread- 



