CLASS GASTROPODA 
315 
including teeth, 4*4 mm. Breadth of median valve, 22; length from sinus 
to beak, 4j4 mm. Breadth of posterior valve, 15; length direct from sinus 
to sinus, 5 mm.; divergence, 135°. Measurements of breadth include the 
insertion plates. (Pilsbry.) 
Type in Philadelphia Academy of Natural Sciences. Type locality, 
Bering Island, Bering Sea. 
Range. Bering Sea and Island, also Kuril Islands. 
Placiphorella velata (Carpenter) Pilsbry, 1878 
Proceedings of the United States National Museum, 1:298, 303, 307; PI. 2, fig. 36. 
Tryon and Pilsbry, Manual of Conchology, 14:306; PI. 66, figs. 6-12. 
Shell roundly oval, broad, rather depressed, quite obtusely angled. Sur¬ 
face lusterless. Light colored along the middle, mainly olivaceous on the 
sides, especially the lateral areas; the central areas variously streaked 
longitudinally with buff, chestnut, and pink. Median valves not beaked, 
marked by growth lines; the lateral areas somewhat raised, having a 
rounded wide diagonal rib and another at the sutural margin, the space 
between them more or less excavated. Central areas having a “false beak” 
or narrow projection forward at the dorsal ridge (only visible when the 
valves are separated). Anterior valve crescent-shaped, sculptured with 
light concentric growth-lines only. Posterior valve small, slightly waved 
inward behind, the mucro far backward, recurved and elevated, the slope 
in front of it concave in profile, unless the mucro is eroded. Interior white, 
slightly blue-tinted. Sinus in valves i to vi represented by a very shallow 
wave, the sutural plates continuous, being connected by a plate which fills 
the sinus like a keystone; in valves vii to viii the sinus is deeper and 
more distinctly angular. Anterior valve having 8 slits, the teeth obtuse, 
short, often bilobed or conspicuously rugose. Central valves having one 
slit, teeth wedge-shaped, thicker at the edges of the slit. Posterior valve 
having a very heavy callus supporting the short, rugose insertion-plate, 
which is interrupted posteriorly by a broad, shallow sinus, and has one 
slit on each side (occasionally two on one side). Girdle very broad in 
front, reddish, fading to yellow toward the outer edge, irregularly and 
sparsely beset with scaly hairs, of which one or two are generally to be 
seen in each suture; a close fringe of short (broken) hairs adorns the 
girdle edge. Length, 50; breadth, 38 mm.; divergence, 135°. Length, 30; 
breadth, 24 mm.; divergence, 130°. (Pilsbry.) 
Type in Academy of Natural Sciences, Philadelphia, No. 35756. Type 
locality, Todos Santos Bay, Lower California. 
Range. Trinidad, California, to Todos Santos Bay, Lower California. 
[917] 
