532 REV. a. P. WHIDBORNE ON SOME FOSSILS 



It is very transverse, inequivalve, with a long escutcheon, the 

 anterior side angulated, the posterior produced and squared, and 

 very slightly gaping. 



It is very similar to Mya depressa, Sow. Min. Conch, t. 418, in 

 general shape, but differs in the squared and flattened anterior part, 

 and in the almost angulated posterior margin. 



Agassiz seems to have changed the name rather unnecessarily, 

 and probably Thurmann's specific name, Tellina incerta, sp., Rom. 

 Yerst. ool. Geb. t. 8. fig. 7, should be restored. 



Pholadomya calljea, n. sp. Plate XIX. figs. 7, 7 a. 



Shell moderately convex, ovoid, transverse, somewhat flattened 

 behind. Umbones small, well defined, rather flattened and very 

 anterior, being often less than one sixth of the diameter from the 

 anterior side. Dorsal side long and straight. Escutcheon very 

 long and lanceolate, bounded by strong sharp ridges. Posterior 

 margin very convex, the line of margin being continued on the 

 inferior side in a fine uninterrupted decreasing curve. Anterior 

 side narrow and slightly convex. Valves meeting at a small angle. 

 The posterior gape moderately long, invading the dorsal side, and 

 very narrow. Surface with small, close, irregular concentric markings, 

 and twelve or thirteen sharply marked but very fine rays, which are 

 simply breaks in the continuity of the surface, curving somewhat 

 backward, and vanishing in the marginal parts. Test very thin. 



Dimensions. Length 22 lines, width 36 lines, depth 16 lines. 



This form is remarkable for its small anterior umbo, fine radiations, 

 and generally symmetrical shape. It seems common in the ironshot- 

 beds of Dundry. There are specimens in the Bristol and Jermyn- 

 Street Museums, and I have obtained several from the quarry near 

 the cross roads at that place. 



Prom Ph. oblita, Morr. & Lye. pt. 2, p. 142, and Lye. Suppl. p. 120, 

 it differs in the character of the umbones, the length of its anterior 

 side, the less rounded form, and, according to the description only, 

 the smaller number of rays. 



It undoubtedly approaches very near to Ph. ovulum, Ag. Et. Crit. 

 t. 3. figs. 7-9, and t. 3 b. figs. 1-6, but seems to me distinct on account 

 of its smaller, more defined and terminal beak, squarer anterior 

 side, and more thread-like rays. Lycett's shell, Suppl. t. 35. fig. 18, 

 is very dissimilar, and Agassiz's original conveys the idea of a more 

 oblique and strongly ribbed form. The variety figured by Mosch, 

 Pal. Suisse, vol. i. t. 20. fig. 4, approaches it most nearly, though still 

 having the anterior side more rounded. 



Some smaller shells from Dundry in the Bristol and Jermyn-Street 

 Museums, and from Bradford Abbas in my collection, agree very 

 fairly with typical specimens of P. ovulum like that figured by 

 Laube, t. 5. fig. 2. They are convex and ovoid, with large and 

 more central umbones (situated two thirds forward), have the side 

 margins curved, and have twelve rather prominent ribs, My own 

 belief is that these belong to a different species from the former ; but 

 considering the immense variability of the Pholadomyce, it is impos- 



