Boston SocieUj of Natural History. 383 



Thracia pubescens, Leach. Mya declivis, Pennant, Maton and 

 Rackett, Wood, Dillvvyn and Brown; Anatina declivis. Brown; 

 Mi/a pubescens, Pulteney, Montagu, and Turton ; Thracia pubes- 

 cens, Blainville, Deshayes, Kiener ; Anatina myalis, Lam., Blainville. 

 It is believed that this shell has never been found on our coast; the 

 shell which Mr. Conrad supposed to be identical with it, proving, on fur- 

 ther examination, to be a distinct species. 



Thracia convexa, Couthouy. Mya declivis, Donovan ; Mya con- 

 vexa. Wood, Turton ; Anatina convexa, Turton, (Brit- Biv.,) 

 Brown; Ligvla distortal Montagu. 

 Thracia corbuloides, Deshayes, Blainville, Lamarck, Kiener. 

 The exterior surface of the valves is not smooth, as described by 

 Deshayes, unless when the granular asperities have been accidentally 

 effaced. 



Thracia plicata, Deshayes, Lamarck, Kiener. 

 Thracia phaseolina, Kiener; Amphidesma phaseoUna, Lam. 

 Thracia similis, Couthouy. Th. testa ovato-oblonga, aspera, al- 

 bida vel ciiierea, subdiaphana, inequilateral!, latere postico lon- 

 giore, truncato et subcompresso, angulo obtuso ab apice ad mar- 

 ginem infero-posticam decurrente ; cardine foveola subtriangu- 

 lari, valva utraque ligamento externe prominulo; intus alba, im- 

 pressionibus muscularibus antice elongatis, quasi clavatis, postice 

 rotundatis; impressio pallii postice valde excavata ; an ossi- 

 culum? Length 1 1, height ^|, diameter /g- of an inch. Hab. 

 Coast of Brazil, not far from Rio Janeiro, whence it was brought 

 by a seaman, containing the animal. 

 In general aspect and its surface it closely resembles T%. corhuloi' 

 des ; but it is destitute of the prominent ridge in the centre of the 

 valves, it is much less inequivalve, and its ligaraentary apophysis is 

 much shorter, broader and more triangular, and its anterior muscular 

 impression is simple instead of double, as in that species, in outline 

 it approaches to Th. phaseolina, but is distinguished by its rough sur- 

 face and by its very marked striae of growth. 



Thracia Conradi, Couthouy. Th. testa albo-cinerascente, ovato- 

 transversa, ventricosa, subsequilaterali, fragili, paullum hiante, 

 margine sinuato, antice rotundata, postice sublruncata, carina ob- 

 tusa ab apice ad marginem infero-posticam decurrente, ligamento 

 externe proininente, interne callo nymphale valva utraque inserto. 

 Length 2i|, height 2/g-, diameter 1-^% inches. Inhabits probably 

 the whole coast of New England. 

 This shell was described and figured by Mr. Conrad, in his " Ameri- 

 can Marine Conchology," as Th. declivis, under the supposition that it 

 was identical with ^lya declivis, Pennant ; and besides mistaking ours 



