C2 BULLETIN OF THE 



Strophomena reticulata Shalbb. 



Sub-triangular, one third wider tban liigh, greatest width at hinge-line. 

 Toothed valve very convex, ventricose, flattened towards the extremities 

 of the hinge-line, slightly alate, most convex point a little more than half 

 the distance from beak to border, depth equal to one third the length of 

 hinge-line, nearly evenly rounded from beak to border, beak minute, 

 projecting a little beyond the hinge-ledge, area one and a half lines wide 

 in a specimen twenty lines broad, fissure broad, without deltidium. Area 

 of socket-valve about one fourth that of toothed valve ; surface deflected 

 to correspond with opposite valve. Surface covered with very numerous, 

 minute, close-set radial striae, crossed by numerous concentric undulations, 

 which near the umbo are small and even ; away from that point they are 

 irregular and larger. — Ellis Bay, Anticosti. Division D, Canada Geologi- 

 cal Survey. 



Strophomena arcuata Shai.ek. 



Shell obscurely trigonal; distance from beak to border two fifths less than 

 length of hinge-line ; greatest width at hinge-line ; toothed valve slightly 

 convex, or nearly flat near the beak, suddenly evenly deflected at two 

 thirds the distance from the beak to border ; surface covered with rather 

 fine, irregular, radial striai, branching several times from beak to border, 

 five to seven in the space of one line on the border. 



This species is a member of the same group with Strophomena eugh/pha 

 of the Wcnlock Lime. — Ellis Bay, Anticosti. Division D, Canada Geo- 

 logical Survey. 



Strophomena anticostiensis Shaler. 

 Syn. Strophomena alternata Billings. 



Outline rather variable, usually evenly semi-oval ; length of hinge-line 

 usually a little greater than from beak to border; sides nearly straight for 

 half the distance from the beak to border ; rest of border gradually curved. 

 Toothed valve slightly evenly convex ; hinge-line narrow ; teeth very slight. 

 Socket-valve flat or nearly so; hinge-line narrow; cardinal process very 

 slight; sockets bordered on the inside by a pointed tooth-like ridge. Mus- 

 cular impressions at all ages indistinct and scarcely impressed. Surface 

 covered with fine punctate markings. Surface of shell with fine strise of 

 two or three sizes, alternately disposed. 



Very closely related to S. alternata Cox., from which it differs in being 

 far more regular ; by the presence of ridges below the sockets ; in wanting 

 the tendency to a sudden deflection, and interior thickening of the bord" r s 

 of the valves. — Heath Point, Anticosti. 



