THRACIA.— Plate I. 



The Corbula-like Thracia. Shell ovately oblong, 

 very inequilateral, rather gibbous, thin, inflated, pos- 

 teriorly eompressly two-angled, and rather squarely 

 truncated, anteriorly tumidly rounded, valves some- 

 what rough and irregular ; everywhere minutely sca- 

 brous, whitish. 



Deshayes, Diet. Class. d'Hist. Nat. vol. xvi. pi. vi. f. 4. 



Hab. Western Mediterranean. 



This species, which is found at Toulon and other parts 

 of the south of France, is intermediate in its characters be- 

 tween the two large species of our own shores. It is more 

 gibbous and shorter than T. pubesceus, and less so than T. 

 eonvexa. 



Species 2. (Mus. Cuming.) 



Thracia cuneolus. Thr. testa subtrigono-oblongd, gib- 

 bosu, postice laliore, tumido-angulata, antice attemtato- 

 rotundata, concent rice irregulariter striata; alba, mi- 

 nute scabrosd. 



The little-wedge Thracia. Shell somewhat trian- 

 gularly oblong, gibbous, posteriorly broader and tu- 

 midly angled, anteriorly atteuuately rounded, concen- 

 trically irregularly striated ; white, minutely scabrous. 



Hab. ? 



The hinder portion of this species, as in T. distorta 

 and rudis, is broader than the front. It has very much 

 the appearance of a borer. 



Species 3. (Mus. Cuming.) 



Thracia siliq.ua. Thr. testa oblongo-quadratd, gibbosi- 

 usculd, utrinque truncate!, latere postico longiore, 

 obscure ang/dato ; alba, minute scabrosd, parum stri- 

 ata. 



The tod Thracia. Shell oblong-square, rather gib- 

 bous, truncated at both ends, posterior side longer, 

 obscurely angled ; white, minutely scabrous, but 

 little striated. 



Hab. ? 



Readily distinguished from other species of the genus 

 by its oblong-square pod shape. 



Species 4. (Mus. Cuming.) 



Thracia Conradi. Thr. testa globoso-ovatd, inflata, 

 subtrigond, postice contractu, attenuato-an/julatd, an- 

 tice tumido-rotundata, raids concentrice rugosis; fer- 

 rugineo-alba. 



Conrad's Thracia. Shell globosely ovate, inflated, 

 somewhat triangular, posteriorly contracted, attenu- 

 ate^ angled, anteriorly tumidly rounded, valves con- 

 centrically rugose ; rusty-white. 



Thracia declivis, Conrad, Amer. Marine Conch, p. 44. pi. 

 ix. f. 2. 



Thracia Conradi, Courthouy. 



Hab. Bay of Massachusetts, U. S. (in deep water). 



This fine species, the largest of the genus, is distin- 

 guished by a broad subglobose form, flexuously attenu- 

 ately contracted and angled on the posterior side. \\ hen 

 first described by Conrad, he was under an impression that 

 it was the Mga decl'wis of British authors ; but it is dis- 

 tinct from any of the species to which that name has been 

 applied ; and where it has been used, its application is 

 mixed up with so much error that it must be abandoned. 

 Thracia Conradi has only been rarely obtained, after a 

 violent easterly storm, or on the breaking up of the ice at 

 Chelsea Beach. 



Species 5. (Fig. a, b, Mus. Cuming.) 



Thracia Myopsis. Thr. testa ovatd, so/ii/iusculd, con- 

 centrice rugoso-striatd ; albidd, vix scabrosd, nunc de- 

 pressd, nunc gibbosiusculd, postice viv angulatd. 



The little Mya Thracia. Shell ovate, rather solid, 

 concentrically roughly striated ; whitish, scarcely sca- 

 brous, sometimes depressed, sometimes rather gib- 

 bous, posteriorly slightly angled. 



Moller, MS. in Mus. Cuming. 



Hab. Greenland. 



With little of the general typical aspect of Thracia, this 

 species has the true dentition of the genus. It is rather 

 solid and depressed, and is very roughly and irregularly 

 striated, with only a faint development of the posterior 

 an ale. 



Species 6. (Mus. Cuming.) 



Thracia conyexa. Thr. testa oblongo-ovatd, valde gib- 

 bosd, postice yradati in attenuatd et tenue angulatd, an- 

 tice suban/pliter rotundatd, valvis irregulariter concen- 

 trice striatis ; laevigata, ferrugineo-albd. 



The convex Thracia. Shell oblong-ovate, very gib- 

 bous, posteriorly gradually attenuated and faintly 

 angled, anteriorly rather amply rounded, valves ir- 

 regularly striated; smooth, rusty-white. 



Mya eonvexa, Wood, General Conch, p. 92. pi. xviii. f. 1. 

 Ligula distorta, Montagu. 

 Anaiina eonvexa, Turton. 

 Aniphidesina concent)//, Fleming. 

 Thracia eonvexa, Courthouy. 



Hab. South-west coast of England. 



The two large species of Thracia inhabiting the shores 

 of Devonshire and Cornwall, are mainly distinguished 

 from each other by their contrast of bulk. While T. pu- 

 bescens is an oblong depressed shell, T. eonvexa is a short, 

 broadly inflated species, the most gibbous of the genus, 

 and it is more contractedly attenuated behind. 



