FAMILY MACTRIDEZ — 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. 
Mactra tellinoides. Conrap, Jour. Ac. Nat. Sc. Vol. 6, p. 258, pl. 11, figs. 2, 3. Ip. Mar. Conch. pl. 14, fig. 2. 
M. id. RussEL, Essex Journ. Nat. Hist. Vol. 1, p. 53. 
Cumingia id. Conrap, Jour. Acad. Nat. Sciences, Vol. 7, p. 234. 
c. id, Govtp, Invertebrata of Mass. p. 56, fig. 36. 
Description. Shell small, thin, fragile, ovate-triangular, nearly equilateral, inflated, broad in 
front, compressed behind, warped, ending ina 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, 0°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. 
(EXTRA-LIMITAL.) 
Genus Gnatuopon, 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. Conrap, Mar. Conch. p. 57, pl. 18. Px. 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. flecuosum. (Conrap, Am. Jour, Sc. Vol. 38, p. 92.) 
Fauna — Parr 6. 30 
