534 KEV. G. P. WHLDBOKKE ON SOME FOSSILS 



This little shell from Bradford Abbas differs from Pholadomya 

 bellula by its peculiar shape and finer markings. The variety of 

 Ph. ovulum given by Mosch in Mem. Pal. Suisse, t. 20. fig. 5, which 

 seems to resemble this shell, chiefly does so because the Swiss speci- 

 men is injured and incomplete behind ; while Ph. paradoxa, Ag., and 

 other species approaching it in general form, are all strongly radiated 

 or keeled. Ph. orbiculata, Rom. Verst. ool. Geb. p. 132, of the Port- 

 landian, is more angulated and oblique, with strong ribs. 



Pholadomya bellula, n. sp. Plate XIX. figs. 10, 10 a. 



Shell small, oval, very convex, slightly transverse. Umbo very 

 large and anterior, elevated, tending rather forward and much 

 incurved. Escutcheon long and large, bounded by very sharp and 

 raised borders. Anterior margin obliquely rounded, inferior arched, 

 and posterior rather narrow and convex. Surface with numerous, 

 regular, deep strise, dividing it into broad, flattened, transverse plaits, 

 the whole covered with crowded finer strise, and crossed by nine 

 lines of strong radiating knots, only visible on the plaits, and arching 

 backwards near the margins. 



Dimensions. Length 10 lines, breadth 13 lines, depth 9 lines. 



There are two specimens of this shell from Bradford Abbas in the 

 Jermyn-Street Museum and one in my own collection. It is a very 

 neat, highly ornamented form, and seems to me well marked, being 

 distinguished from Ph.- Heraulti, Ag. (=Ph. Murchisoni, Sow., pars), 

 by its defined escutcheon, and from Ph. socialis, Chapuis (non Morr. & 

 Lye), Eoss. Lux. Suppl. t. 12. fig. 1, by that and by its knotted ribs. 



The Liassic species, Ph. Simpsoni, Tate and Blake, Yorkshire 

 Lias, t. 12. fig. 8, which is stated to com between Ph. Dewalquea 

 and Ph. ambigua, is smooth behind, and these three shells have 

 unkeeled escutcheons. 



From Ph. concinna, Ag. loc. cit. t. 7 a. fig. 1-6, it is distinguished 

 by its much more elevated beaks. 



Pholadomya spatiosa, n. sp. Plate XIX. fig. 11. 



Shell large, ovate, deeply convex, transverse. Umbo large and 

 prominent, round and anteriorly curved, considerably raised above 

 the hinge-line. Escutcheon small and indistinct, without bounding 

 ridges. Dorsal side straight ; posterior side broad and flatly convex ; 

 inferior side slightly convex and oblique; anterior side rather 

 attenuated, rounded above and oblique below. Test thin. Surface 

 covered with very numerous and irregular concentric striae, which 

 nodulate the oblique ribs, of which eight are rather prominent, and 

 reach the margins in a backward curve (the second front one being 

 the largest), and two, one each side, are more indistinct and only 

 visible near the umbo, so that the lateral portions of the shell are 

 smooth. Gape very long and narrow. 



Dimensions. Length Scinches, breadth 4 J inches, depth 2^- inches. 



There are fine specimens in the Jermyn-Street Museum, in my own 

 collection, and especially in the British Museum, from the ironshot 

 beds of the Humphriesianus-zone of Dundry. 



