TRIBE PHOLADARIA. 9 



trically striated : dorsal edge posteriorly reflected and inflated : 

 with two anterior, dorsal, sub-ovate, accessory valves ; the epidermis 

 anteriorly running down upon two flattened valves and then a cal- 

 careous tube conspicuous at the extremity. ■^^^.. 1 Jg. — TF. Colum- 

 bia. Very like Papt/racea: ike intermediate ages loithoiit the tube. 



P. Papyracka.* Turt. B. p. 2. t. \.f. 1 to A.—Som. G.— 

 Reeve, t. 24./. ^.~W. S. t. \. f. 1. Ovate oblong, closed and 

 very obtuse posteriorly, open and truncated anteriorly, posterior mar- 

 gin reflected at the hinge into a thin nearly erect narrow plate ; 

 dirty white, divided by a longitudinal groove ; anteriorly with de- 

 pressed concentrical lamellse, posteriorly towards the hinge with close 

 obliquely curved toothed thin ridges, the remaining portion nearly 

 smooth : nacreous white within. — Youvg. (P. Lamellata. Turt. 

 Biv. t. \.f. 5, Q—W. S. t. \.f. 2.)— Without the smooth space 

 at the posterior ventral edge, and consequently with a large oval 

 gape. 1^. — Eyigland. 



P. CuRTA. Sow. Z. P. 1834. Oval, anteriorly acuminated, 

 posteriorly rounded : valves divided by a transversely grooved band ; 

 the posterior area obliquely divided, the dorsal portion with radia- 

 ting wrinkles and transverse strise, the ventral thinner and sub- 

 inflated : anterior surface with concentric strise : accessory valve 

 solitary, posterior dorsal, sub-acaminated at the ends and con- 

 tracted in the middle : upper and lower edges with a horny testa- 

 ceous epidermis which on the dorsal surface is anteriorly forked. 

 '2^' — ir, Colum.bia. 



P. Cornea. Soiv. Z. P. 1834. Oblong, thin, posteriorly 

 rounded, anteriorly obtuse : a thin horny epidermis ; valves divided 

 by a band ; posterior area obliquely divided, the dorsal portion 

 being rather rugose, the ventral smooth : anterior surface larger 

 and smooth ; with three accessory valves, the posterior dorsal one 

 rounded, and sub emarginated anteriorly : anterior gape large. \-§ - 

 — W. Cohnnhia. 



P. TuBERcuLATA.* Turt. B. p. 5.t. 1. /. 7, 8. — W. S. t. 

 l.y. 3. Oblong with the ventral margin posteriorly sinviated, but 

 not forming a beak at its extremity ; gape nearly orbicular : tbe 

 transverse rough striae disappearing anteriorly after crossing the 

 longitudinal groove : a single accessorial valve and a rough tubercle 

 on the edge above the teeth, f . . 1^. — England.'^ 



^ In this genus we must include Turton's 



XYLOPHAGA. 



Orbicular; (eqidvaJve, inequilateral, posteriorljj gaping, with two 

 sub-triangular testaceous accessor)/ pieces, a minute cardinal 



