TRIBE CORBULACEA. lfj 



10(>. — W. t. 5.f. 97. Oblong, anterior side elongated, with two 

 very obtuse keels near the dorsal edge, somewhat beaked and slightly 

 truncated : tooth in the flat valve small and blunt ; hinge margin 

 slightly arched, recurved. T 7 ^.. If. — Europe. 



P. Oblonga. Sow. Sp. Con. f 10. Longer than Kostrata, 

 thin: anterior side rather beaked, with two very obtuse keels and 

 the hinge margin nearly straight ; ligament and tooth of the flat 

 valve very small. ^.. 1^. — Gramberoon. 



P. Depressa. Sow. Sp. Con.f. 11, 2. Ovate, more depressed 

 than the other species ; anterior side dilated ; valves nearly equally 

 flat, two distinct teeth in the flatter, and one very large in the deeper : 

 dorsal edge somewhat arched, slightly recurved. -J. . 1 T ^. — Pacific. 

 P. Glacialis. Leach, in Ross. voy. — Sow. Sp. Con.f. 4, 5, 

 6. Nearly oval, dorsal edge nearly straight; posterior side rather 

 produced, obtusely angular ; beak nearer the centre than in Obtusa : 

 tooth in the flat valve very small, f . —Nortli Seas. 



P. Flexuosa. Sow. G. — Sow. Sj). Con.f. 1,3,4,5. Oblong, 

 rather more gibbose than in general ; anterior side elongated, sub- 

 rostrated ; ventral edge flexuous ; dorsal bicarinated, rather arched 

 and recurved: a rather short tooth, and an elongated, internal sub- 

 marginal plate on the anterior side of the flatter valve. -jo-tV — 

 Red Sea. 



P. Unguiculus. Sow. Sp. Con. f. 16, 7. Oblong, rather 

 depressed ; anterior side narrower, rather produced, dorsal edge 

 nearly straight with two obtuse keels from the umbo to the end of 

 the beak : posterior side rounded or sub-truncated. 3 T ^ 6 . 



P. Trilineata. Say. in Jonrn. A. N. S. Phil. 2. — Conrad. 

 Am. C. t. 11./ i.— P.'Nasuta. Sow. Sp. Con.f 18, 9. Rather 

 lengthened, deeper valve with a flexuous margin : anterior side of 

 both valves beaked, their dorsal edge arched, recurved : posterior 

 dorsal edge with a small projecting wing-like appendage : a distinct 

 tooth and an internal elongated sub-marginal plate in the anterior 

 side of the flatter valve ; two obtuse rather obsolete ridges in both 

 valves from the umbones along the anterior dorsal edge. t 3 q . . I -fo. — 

 N. America. 



P. Brevifrons. Sow. Spec. Con. t. 2. f. 25, 6. Elongated, 

 very thin, white and hyaline ; posterior side the shorter, rounded 

 and sub-angulated dorsally : anterior side the longer, beaked and 

 sub-truncated ; dorsal edge straight, ventral rounded ; a solitary 

 and very small tooth in the flattened valve. 7 ^J 8 . — Panama. 



P. Arcuata. Sow. Spec. Con. t. 2.f 27 9 8. Ovate, thickish, 

 opaque, pearly ; posterior side the shorter, rounded, anterior beaked: 

 dorsal edge arcuated, ventral rounded : an obsolete impressed groove 

 running from the umbo to the ventral margin. J-. . 1 . — W. Columbia. 

 P. Discors. Sow. Spec. Con. t. 2.f. 29, 30. Elliptic, depressed, 

 whitish, opaque : posterior side the shorter, anterior broader ; 



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