30 NEW UXIOXID.E OF THE 



prominent; ligament very long, rather thick and very dark brown; epidermis blackish, 

 minutely striate, shining toward the beaks, with very indistinct marks of growth ; 

 umbonial slope slightly raised and very obtusely angular ; posterior slope very long 

 and but slightly raised ; cardinal teeth small, compressed and conical; lateral teeth 

 very long, lamellar and very slightly curved ; anterior cicatrices distinct and well 

 impressed ; posterior cicatrices large, confluent and slightly impressed ; dorsal cicatrices 

 ])laced above the centre of the cavity of the beaks ; cavity of the shell not deep, but 

 very wide ; cavity of the beaks very small, scarcely perceptible ; nacre purplish and 

 very iridescent. 



Soft 2M^'(-^- — Brancldal vtenis probably occupies the whole width of the outer 

 branchia?, as ova were found partially deposited in nearly the whole of it. Branchia' 

 very wide, nearly straight on the lower margin, inner ones much the larger, free about 

 one-half the length of abdominal sack. Palj)i rather large, transverse, angular at the 

 posterior end and united nearly half way down the posterior edges. Mantle rather 

 thin, brownish, with a thickened border, colored on the edge. Brancldal opening very 

 large, with numerous small brown papilla?. A7ial opening with numerous, very minute 

 brown papillas on the inner edges. Super-anal opening very small and united below. 

 Color of the mass whitish. 



Remarks. — Among quite a number sent to me by Mr. Downie about one-half were 

 females, but no one had the ova fully developed in the branchial uterus, so that the 

 embryonic form was not ascertained. Some of the specimens were less cylindrical 

 tlian the one figiu'ed. There were no very young individuals, and the beaks of all 

 Avere more or less eroded. Some of the younger had obscure rays. The character of 

 the undulations of the tips could not, therefore, be ascertained. In outline it is near 

 to naviculoides (nobis), but it is more cylindrical and has a much darker epidermis, 

 being nearly or quite black. In all the specimens the color of the nacre was light 

 purple — none had white or salmon color. It has somewhat the aspect of a very wide 

 luguhris (nobis), but it is much wider and not so compressed. 



I name this after a friend of Mr. Downie, to whom we are under obligations for his 

 assistance. 



Uxro Neislerii. PI. 26, fig. 93. 



Testa regulariter plicata, quaJrata, inflata, ad latere subplanulata, valde insequilaterali ; valvulis crassis ; 

 natibus prpminentibus tumidisque ; epidermide nigricante, valde striata; dentlbus cardinalibus magnis, 

 crassis, crenulatis, in utroque valvulo duplicibus ; lateralibus crassis, sublongis curvisque; margarita 

 argentea et vald^ iridescente. 



Shell regularly plicate, quadrate, inflated, flattened at the side, very inequilateral ; 

 valves thick ; beaks prominent and thick ; epidermis nearly black and much striated ; 

 cardinal teeth large, thick, crenulate and double in both valves ; lateral teeth thick, 

 rather long and curved ; nacre pure white and very iridescent. 

 Proc. Acad. Nat. Sei., 1858, p. 1C5. 



