75 



Panop;ea generosa. Testa magna, ponderosa, calcarea, 

 sub-quadrilateralis, concentrice undulos o-plicosa, epidermide ru- 

 goso flavido induta, antice rotundata, postice truncata et valde 

 hians ; umbonibus submedianis, acutis, elevatis, undulatis : cardo 

 gracilis, dente elevato oblique triangulari iustructus : cavositas ad 

 apicem profunda ; cicatrice musculari lato, bene impresso ; sinu 

 siphonali minime profundo. Long. 6 ; alt. 4 ; lat. 3 poll. Hab. 

 Puget Sound, Oregon. 



This large species stands by the side of P. Aldrovandi, but is 

 distinguished by the form of the anterior extremity. 



Mya pr^cisa. T. M. truncates similis, calcarea, epidermi- 

 decorneo induta, ovata, antice rotundataet ventricosa, postice 

 angustata, compressa et truncata ; cardo dente trapezoideo, 

 latiore quam elevato, postice declivo instructus; linea palleali 

 angusta, crenata ; sinu siphonali profundo, arcuato ; cicatrice 

 anteriori elongato, falciformi. Long. 2^-; lat. 1 ; alt. 1£ poll. 

 Hab. Puget Sound. 



Differs from M. truncata in being more narrowed posteriorly, 

 more rounded anteriorly, more inflated at the umbonal slope, in 

 its narrow palleal impression and deeper siphonal sinus, and 

 more particularly in having the tooth slope backwards. 



Mactra deluta. T. tumida, ovato-rotundata, hiantissima, 

 sordida, epidermide tenui deluto, oblique corrugato induta, con- 

 centrice undulata ; umbonibus submedianis, tumidis, incumben- 

 tibus, contiguis ; margine dorsali utroque declivi ; margine ven- 

 trali rotundato; lateribus obtusis : cardinis fovea ligamentali 

 profunda ; dente V-formi gracili, ramis inequalibus ; dentibus 

 lateralibus brevibus, trigonis, compressis ; sinu siphonali prope 

 centrum valvae obducto. Long. If; alt. If; lat. l T \j poll. Hab. 

 New Zealand. 



The external appearance is rather that of a rude Venus, and 

 has fewer angularities than any other Mactra. It is also peculiar 

 for its very wide gape. 



Mactra cuneola. T. parva, crassiuscula, rudis, ovato-cune- 

 ata, albida, epidermide stramineo induta, concentrice striata; 

 umbonibus submedianis, tumidis, acutis, anteversis ; latere 

 antico angustato, subacuto ; latere siphonali breviori, tumidiori, 

 subtruncato : area cardinalis minima ; fovea ligamentali indis- 



