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is 
— 
Description of a New Species of Thracia. — 145 
oa a : 
Arr. XIII.—Description of a New Species of Thracia, 
ae Prof. Chem. and Nat. Hist. Middlebury | } 
ik Pcacts INEQUALIS. eg 
T. testa fragili, per-inequilaterali, per-inequivalvi, i 
striata, Postice truncata; valva sinistra subplanulata; altera per- 
convexa; callo siymspliali pomhlenrtigiem, anterius —— Ossi- 
culo lenato; semicirculari. | 
Shell white, very thin, before broadly and behind BO 
truncate, very itiequiliitetak and inequivalve, much deflected to the 
left anteriorly ; with the strie of growth unequal, numerous and 
crowded at the extremities, where, under a magnifier, the surface 
appears shagreened by minute wrinkles of the strie ; epidermis 
very thin, brownish, thicker at the extremities; left valve nearly 
flat, with five obtuse angles radiating from the beak ; right valve 
much larger and very convex, emarginate in the pie 4 of the 
posterior truncation, with a groove and elevated umbonial angle 
defining the areolar region, its inferior margin sinuous; beaks 
small, pointed, lamelliform, the right one moderately etenrated 
for the reception of the other ; nym pheal callosities spoon-shaped, 
very much produced forwardl nd inwards; ossiculum semicir- 
cular and lunate, with an im on on the cantre’of each side, 
but much deeper on as side, situated between the s aped 
apophyses and the dorsal bi 
Dimensions.—. —Length 1. i height 75 inch 
inch ames of esta ic.” wae | 
binet of Middlebury College. a 
a Gulf of Mexico. 
Remarks.—A single specimen of this interesting species was 
presented to the cabinet of this college by the Rev. Wm. T. Ham- 
ilton, of Mobile, Ala. It is remarkable for the disparity of the 
valves, the irregularity of its form, and the sharp lamelliform beaks. 
=m, = ae neo" 1 Seat ee Guar diiataiee 
19 
