FAMILY MACTRID.E CUMINGIA. 233 



GENUS CUMINGIA. Broderip and Sowerby. 



Shell ovate, inequilateral, equivalve. A shallow spoon-shaped cardinal tooth, and a single 

 small tooth by its side, in each valve ; and a strong lateral tooth on both sides in one valve 

 only. Palleal impression with a large sinus. 



CUMINGIA TELLINOIDES. 



Maclra lellinoides. Conrad, Jour. Ac. Nat. Sc. Vol. 6, p. 258, pi. 11, figs. 2, 3. Id. Mar. Conch, pi. 14, fig. 2. 



M. id. Russel, Essex Journ. Nat. Hist. Vol. 1 , p. 53. 



Cumingia id. Conkad, Jour. Acad. Nat. Sciences, Vol. 7, p. 234. 



C. id. Gould, Invertebrata of Mass. p. 56, fig. 36. 



Description. Shell small, thin, fragile, ovate-triangular, nearly equilateral, inflated, broad in 

 front, compressed behind, warped, ending in a rounded point. Beaks raised, with a small well 

 defined area in front. Surface with concentric incremented lines, which are sharp and ele- 

 vated, and crossed by microscopic radiations. In front of the cartilage pit in each valve is a 

 linear tooth, forming part of its wall, and at its side a pit for the reception of the corresponding 

 tooth : lateral teeth distinct in the right valve, but wanting in the left ; the anterior one longest. 

 Palleal impression far within the shell, with a broad deep sinus. 



Color, bluish white ; within bluish white. 



Vertical axis, 0'45; transverse ditto, - 6. 



I am indebted to Dr. Gould for the description of this species, which I have not seen, but 

 which is very probably to be found on the coast of this State. 



( EXTRALIMITAL. ) 



Genus Gnathodon, Gray. Shell thick, nearly oval, equivalve, inequilateral, covered with an oliva- 

 ceous epidermis ; umbones distant. An acuminated cardinal tooth and two lateral teeth, the 

 posterior elongated, the anterior uncinate in one valve ; in the other, two acuminate and two 

 lateral ones, the posterior of which is elongated, and the anterior wedge-shaped. Palleal 

 impression with a small sinus : ligament internal, in a deep pit. 

 G. cuneatum, Sowerby. (Gray, Loud. Mag. Vol. 1, p. 376, fig. 34. Rangia, Desm. Lin. Soc. Bord. 

 Vol. 4, p. 58. Conrad, Mar. Conch, p. 57, pi. 13. Pl. 25, fig. 267 of this work ) Shell very 

 solid, inequilateral, subcordate, oblique : beaks prominent, incurved, often eroded ; posterior margin 

 subacute, anterior rounded; lunule heart-shaped, circumscribed by an obsolete raised line; left valve 

 with two teeth on one side of the deep ligament pit, the anterior smallest, the outer with a broad 

 lamellar tooth parallel with the posterior slope. Color, light olive brown. Vertical axis, 1 • 4 ; 

 transverse, 1-7; diameter, 1*1. Mobile. 

 G. flexuosum. (Conrad, Am. Jour. Sc. Vol. 38, p. 92.) 



Fauna — Part 6. 30 



