LaMELLIBRANCHIATA, | DEVONIAN MOLLUSCA. 395 
saw nothing analogous. On first sight it most nearly resembles the D. wnilateralis, but is easily distinguished 
by its greater depression, which renders nearly obsolete the strong diagonal ridge of that species : it is also well 
distinguished by the character which first struck my eye, of the greater length of the hinge-line, its being more 
nearly parallel with the ventral margin, the less oblique truncation of the posterior end, and the consequently 
shorter posterior margin. 
Position and Locality—Common in the sandstone of Baggy Point, North Devon; and in the schists 
quarter of a mile S. of Marwood. 
Dorapra Harpinar (Sow. Sp.) 
Ref. and Syn. = Oucullea Hardingi Sow. Geol. Trans. Qnd Series, Vol. V. t. 53. f. 26, 27. 
+ C. trapezium id. id, t. 53. f. 24. 
Sp. Ch._—Transversely oblong, anterior end nearly one-third the length of the shell, narrowed, elliptically 
rounded, both valves very gibbous, left valve most so, and with the most prominent beak; diagonal ridge 
obtusely rounded ; diagonal slope flattened, with a shallow radiating sulcus rather nearer the diagonal ridge 
than its middle, extending from the beak to the margin, which it slightly sinuates; ventral margin slightly 
convex, and slightly sinuate in the front of the diagonal ridge; posterior margin slightly sinuous, forming an 
angle of about 80° with the ventral margin; surface marked with small obsolete, irregular, concentric wrinkles, 
and rather strong lines of growth. Length of rather small specimen one inch seven lines, proportional width 
from beak to ventral margin, at right angles thereto, ;{;, depth of both valves =, length of anterior end %, 
width of posterior end %, length of hinge-line =, width of the double area about one line. 
This species is easily distinguished from the C. wnilateralis by its longer anterior side, more obtuse diagonal 
ridge, narrower posterior end, from the respiratory angle being less obliquely produced, and the shallow, 
divisional hollow along the posterior slope. The posterior cardinal tooth is only seen in one-of the specimens 
of this species, the hinge-line of which presents numerous parallel pits at right angles to its length, as in 
Gervillia. The original type-specimens of Sowerby’s C. trapezium is a large crushed example of this species, 
differing in no other respects from ordinary specimens. 
Position and Locatlity—Abundant, but not so common as the C. wnilateralis in the sandstone, Marwood 
Quarry, near Barnstaple. 
DoLABRA UNILATERALIS (Sow. Sp.) 
Ref. and Syn. =Cucullwa unilateralis Sow. Geol. Trans. 2nd Series, Vol. V. t. 53. f. 23. = Cucullaa 
amygdalina Phill. Pal. Foss. f. 66. 
Sp. Ch—When young obliquely rhomboidal, when old becoming very obliquely ovate from the prolon- 
gation of the respiratory angle; valves very gibbous, left valve considerably more so than the right; beaks 
very large, obliquely tumid, approximate; rather more than one-third of the hinge-line in front of the beak ; 
posterior slope flattened, very steeply inclined, forming an obtuse diagonal ridge with the body of the shell; 
posterior margin nearly straight, obliquely truncated ; respiratory angle narrow, rounded; anterior and yentral 
margins uniformly arched, surface marked with concentric, obtuse, irregular lines of growth. Length from 
anterior end to respiratory angle of average-sized specimens two inches, proportional width from beak to 
ventral margin at right angles =, depth of left valve =, length of hinge-line ;{,, length of posterior mar- 
gin 2%, length of anterior side 7, angle between posterior and ventral margins about 65° in young, varying 
in old to 60°, cardinal area rather more than two lines wide in the middle, gradually narrowing to each end. 
The impression on the posterior slope of one of the specimens examined and figured by Mr Sowerby, 
supposed by him to be the internal impression of the peculiar internal lamina of Cucul/wa, is manifestly the 
remains of a crush during the life of the animal, being crossed by the lines of growth ; it is, besides, straight, 
and diverging, having no analogy of shape or direction with the hood-shaped plate bounding the muscular 
impressions of Cucullwa. 
3 E2 
