244 NEW-YORK FAUNA — MOLLUSCA. 
posterior end. Surface with a thick epidermis, and coarsely wrinkled concentrically. Hinge 
with two curved cardinal teeth, with a thickened callus behind, to which the ligament is 
attached ; two teeth, or rather a bifid tooth, in the other. 
Color. Epidermis straw-colored ; darker at the extremities. 
Vertical axis, 0°8 - 1:5; transverse ditto, 2°6 —4°0. 
This species occurs along the southern coast, and extends northwardly nearly to Cape 
Cod. It has been observed near Rye, Westchester county, by Dr. J. C. Jay. 
(EXTRA-LIMITAL.) 
S. fragilis, Montagu. (S. centralis, Say. Ac. Sc. Vol. 2, p. 316. 8S. fragilis, Conran, Conch. pl. 
4, fig. 1. Govxp, p. 31.) Shell small and delicate, transversely oblong-ovate, compressed, 
arcuated, equilateral. Hinge with two large ascending teeth in each valve; in the left valve, one 
is broad and emarginate at the tip. Color: epidermis yellowish. A reddish purple band passes 
from the beaks across the shell. Vertical axis, 0+5; transverse ditto, 1*5-2°0. Massachusetts, 
Southern coast. 
GENUS MACH/ERA. Gould. 
Animal not much larger than the shell. Edges of the mantle pectinated from near the siphon 
to the hinge, except where they pass over the foot: similar appearances along their inner 
submargin near the siphon. Labial appendages long, extending quite across the foot, 
pointed. Branchie extending to the opening of the siphon, and embracing about half the 
breadth of the foot. Foot hatchet-shaped, dilating towards its extremity, which is obliquely 
truncated. Siphons united at their tips, which have scattered hairs. Shell transversely 
oblong-oval, compressed, inequilateral, moderately gaping: beaks minute. Hinge with 
three diverging cardinal teeth in the left valve ; the middle one bifid ; the third compressed, 
delicate, taking the direction of the margin, or obsolete: on the right valve, two entering 
between those of the opposite valve. Within, usually crossed by a strong longitudinal 
rib. Muscular impressions joined by a deeply sinuous palleal line : ligament prominent. 
Macua&ra cosratTa. 
PLATE XXXII. FIG.301. a. 3. 
(STATE COLLECTION.) 
Solen  costatus. Say, Jour. Acad. Nat. Sciences, Vol. 2. p. 315. 
Solecurtus id, Ip. Am. Conchology, pl. 18. 
Ss. td. Conrap, Am. Mar. Conch. p. 21. pl. 4, fig. 2. Gouxp, Invertebrata of Mass. p. 34, 
Description. Shell thin and fragile, oval-oblong, much compressed; ends unequally rounded; 
basal margin regularly and widely curved. Beaks very minute, and at the anterior fourth ‘of 
