the Family Osteodesmacea. 147 
number varying somewhat in different individuals. The 
cardinal edge is delicate, and each valve is furnished 
with a small horizontal, triangular, tolerably thick pro- 
jecting support, for an internal ligament, which is 
slightly visible on the exterior. Externally, the valves 
are smooth, white and polished, like the interior. "The 
anterior muscular impression very superficial, elongated, 
and very narrow, is united. to the posterior, which is 
small and rounded, by a — — strongly ex- 
cavated posteriorly. . 
Length one and a half ESA height one inch. 
This species, wholly white, is exceeding rare in col- 
lections. I have never seen but two valves, and their 
locality is unknown., A fossil analogue is found in the 
vicinity of "cUm but is quite rare.  (Deshayes.) 
Tamora PHASEOLINA. 
Th. testà ovato-oblonga, transversà, sabdeprosi; sibl) 
_inæquivalvi, alba, subdiaphana, transversim tenué striatà, latere pos- 
tico breviore , angulato, truncato, 
Amphidésma phaseolina, Lam. Anim. sans Vert. 
V. p. 464, ed. 1816. 
"Thracia phaseolina, Kiener, Iconog., Gen. Tura- 
cra, p. T, ref. ad. tab. 1, f. 2, Mont. exclus. 
Description. Shell ovate, oblong, transverse, sub- 
equilateral, inequivalve, beaks small, the left one slightly 
notched. The valves are white, sub-diaphanous and 
‘smooth, indistinctly marked with ‘strie of increase, 
rounded at the anterior side, strongly truncated at the 
posterior side; this side is bounded externally by an 
