NO. 1985. ySW SPECIES OF SILURIAN FOSSILS— WILLTAMS. 343 



ACTINOPTERIA FORNICATA, new species. 

 Plate 30, figs. 14, 15, 16. 



This species resembles A. heUa in its general form, but differs from 

 it by its greater conTexity, more prominent and narrower beak and 

 elevated narrow body of the left valve. The type-specimen is smaller 

 than the majority of specimens referred to the same species from the 

 same locality and is chosen as type on account of showing both valves. 

 Left valve: The beak of the left valve is pointed, arching over the 

 hinge and rapidly rises to the high arched narrow body which 

 broadens gradually as it proceeds to the front; at the middle of the 

 shell the anterior and posterior slopes are nearly symmetrical. The 

 wing is flattened and produced at the cardinal margin into a short 

 accuminate point which extends slightly beyond the postero-ventral 

 angle. The anterior ear is prominent, arched at its center, and 

 acutely pointed and separated from the body by a shallow sulcus. 

 E-adiating lines sharp and fine over the umbones become broader 

 toward the front and are restricted to the body portion of the shell; 

 they are crossed by finer concentric lines which cover the whole 

 surface, including the ear and wing, where they are more or less 

 laminose. The right valve is low-convex; its beak is small but 

 rather sharply defined and rises scarcely beyond the hinge line: the 

 body is gently convex and is separated from the nearly flat ear by a 

 shallow sulcus. The surface of the right valve is without radiating 

 lines and shows some faint concentric lines. Dimensions: Hinge 

 line, 25 mm.; from hinge to ventral margin perpendicular to the 

 hinge, 15 mm.; from beak to postero-ventral corner, 20 mm. Thick- 

 ness of the two approximated valves, 10 mm., of which about 7 

 belongs to the left valve. Two large specimens referred to the same 

 species are 25 and nearly 30 mm. along the hinge line. 



Formation and locality. — Shales of Pembroke formation on the 

 northwestern shore of Young's Cove, Pembroke Township, Wash- 

 ington County, Maine (loc. No. 5.1.4B). Cat. No. M13S5. 



Eolotype.—Csit. No. 58965, U.S.N.M. 



ACTINOPTERIA DISPAR, new species. 

 Plate 30, figs. 20, 21. 



This species, of wliich left valves only are in evidence, is of the 

 general t3'pe of A. hella but differs from it in its more erect form. 



Shell elongate-ovate, erect, moderately convex; beak strong, rather 

 wide and overarching. Body of shell low-convex, elongate, spatu- 

 late, its axis nearly erect, inclined shghtly backward. Posterior and 

 anterior margins nearly straight and subparallel, greatest width at 

 hinge margin. Posterior wing triangular, flattened, and terminating 



