24 PANDORID/E. 



Searles Wood) no well determined fossil species have 

 been met with in anv formation older than the Paris 

 basin. The animal was included by Poli in his genus 

 Hypogcsa. For the shell Bolton proposed Calopodium, 

 and Brown Trutina. 



Pandora in^quival'vis"*, Linne. 



Tellina in&quivalvis, Linn. S. N. p. 1118. P. rostrata, F. & H. i. p. 207, 

 pi. viii. f. 1-4, and (animal, as P. obtusa) pi. G. f. 10. 



Body transparent, with flake- white specks ; mantle thin, 

 scarcely (if at all) protruded : tubes short, separate although 

 nearly close together, issuing from a very slight, pellucid and 

 membranous sheath, which extends beyond the shell at its 

 posterior end, and is partly continued round the edges ; orifices 

 wide, plain but jagged : gills unequal-sized, the upper being 

 twice the size of the lower pair, which are almost rudimentary ; 

 they are pectinated by the blood-vessels on both surfaces : 

 imlps very short, reddish-brown, striated transversely, and 

 often overlapping each other: foot white: liver green: ovary 

 red-brown. 



Shell irregularly triangular, right or convex valve consider- 

 ably overlapping the other ; it is variable in thickness and opa- 

 city, and somewhat glossy : sculpture, slight plait-like marks of 

 growth, and sometimes a few imperfect longitudinal wrinkles on 

 the flat valve, which are only perceptible in front and appear to 

 radiate from the beak : colour pearl-white ; epidermis filmy 

 margins rounded or obtusely angular on the anterior side 

 forming in front a nearly semicircular but oblique curve 

 which is prolonged at the posterior side to a blunt point 

 dorsal margin straight or slightly incurved, furnished in the 

 right valve with a double furrow, and in the left with a double 

 ridge, both of which extend from the beak to the posterior end 

 or point : beaks extremely minute and tubercular ; umbones 

 not prominent : cartilage horn colour, running inwards on the 

 posterior side at an acute angle with the dorsal margin, and 

 occupying a groove in each valve, the sides of which are thick- 

 ened : hinge-line straight, or more or less incurved : hinge- 

 plate long, strengthened by a rib in the left valve, that fits into 

 a slight furrow in the opposite valve : teeth, in the right valve 



* Valves unequal in size. 



