468 MOLLUSCA. 
TTEREBRATULA CAURINA (Could). 
T. parva, fusco-cinerea, transversa, convexiuscula ; quincuncialiter punc- 
tata, costis angulatis ad duodecim interdum bifurcatis radiata ; mar- 
gine ventrali circulart, flecuoso; apice acuto, rectangulart ; lateribus 
rectilineartbus, incumbentibus ; rostro brevi, vix curvato; Soramine 
circulart, interrupto: apophysis branchialis tenuissima, angustata. 
Terebratula caurina, Goutp; Proceed. Boston Soc. Nat. Hist., iii. 
347. Dec. 1850. Expedition Shells, 97. 
SHELL small, dusky ash-colour, moderately convex, rather broader 
than long; ventral margin rounded, with a central broad flexure, and 
corresponding depression in the smaller, and angulation of the larger 
valve; surface with twelve or more obtusely angular, radiating ribs, 
gradually enlarging, and sometimes bifurcating ; interspaces and ele- 
vations about equal; the whole with microscopic opaque dots; small 
valve having the apex a little pointed, and the posterior outlines other- 
wise rectilinear, and forming a very obtuse angle; large valve forming 
about a right angle at beak, but with the lateral outline concave, and 
the margin incumbent, forming a broad nearly flat area; beak but 
little raised, pointed; the ligament aperture very large, circular, a part 
of its margin formed by the apex of the small valve; internal apophysis 
similar to that of ‘1. pulvinata, but much more delicate and thread- 
like, the two branches curving towards each other so as almost to touch. 
Length half an inch; breadth eleven-twentieths of an inch. 
Inhabits Puget Sound, Oregon. 
T. australis is closely allied, but is more elongated and more con- 
vex; the beak is also elongated and the ribs are less prominent. 
Figures 582, 582 a, lateral views of the shell; 582 0, edge of the shell, 
in outline; 582c, sculpture ; 582d, 552, views of the apophysis. 
