BIVALVIA. 43 



is sinuated ; the anterior side has a large, rounded, but compressed lobe ; the posterior 

 border is very convex, and is curved elliptically ; the surfaces of the valves have a few 

 large, irregular and distant plications. 



The length is twice the breadth, and two fifths greater than the convexity of the united 

 valves. 



The very inflated figure, the curvature of the valves, and the distinct anterior broad 

 sulcation, distinguishes it from other Jurassic species ; some specimens, smaller and appa- 

 rently younger, cannot perhaps be distinguished from Modiola reniforniis, Sow., for the 

 species varies in the length, curvature, and convexity. 



Geological Positions and Localities. This species is figured upon the authority of 

 specimens in the Museum of Practical Geology, which are stated to have been collected in 

 the Cornbrash of Melbury Osmond. It is common in the Inferior Oolite of the soxithern 

 counties. 



CUCULL^A CORALLINA. Tab. XXXIX, fig. 3. 



CUCULL^A OBLONGA, Phil. Geol. York., i, t. 3, fig. 34, non Sow. 



CORALLTNA, Damon. Geol. Weymouth, Suppl., pi. 4, fig. 8. 



Testa inflata, subrhomboidali, subatquilaterali, umbonibus magnis mediants acutis, 

 incurvis, latere postico abbreviato abrttpte truncato, area cardinis brevi, superficie lineis 

 longitudinalibus crebris, irregularibus aliis radiantibus subobsoletis decussata. 



Shell much inflated, subrhomboidal, nearly equilateral; umbones large, mesial, 

 incurved, elevated, slightly oblique, and nearly in contact. 



The anterior side is produced and rounded, the posterior side is very short, abruptly 

 truncated, slightly excavated, and separated from the other portion of the surface by a 

 strongly defined subacute angle ; the hinge area is short and not wide ; the surface has 

 densely arranged, irregular, longitudinal lines, decussated by others radiating, but much 

 less clearly defined. 



Dimensions. Height, three fourths of the length . 



A very short, tumid, abruptly truncated Cucullsea, possessing these characters in a greater 

 degree, and less oblique than any of the shorter examples of C. oUonga, Sow. ; the latter 

 shell has also several large, widely separated, radiating lines upon the anterior side, of which 

 our species is destitute. It appears to be identical with Cuculltea ohlonga, Phil., from the Coral 

 Rag, at least with the more short examples of that species, for the Coral Rag shell presents 

 great variability in its general figure, more especially in that of the posterior side, and it is 

 easy to obtain specimens which insensibly connect the shorter with the more lengthened 

 and oblique forms ; it rarely happens that the surface ornamentation can be discovered, 

 but the portions of the surface obtained agree with that of the Cornbrash shell. 



Geological Positions and Localities. Cucullaa corallina occurs rarely in the Cornbrash 

 of the Yorkshire coast, but is abundant in the Coral Rag of Pickering and of 

 Oxfordshire. 



