140 ANATINID^E. 



We have named Periploma, but are not aware that any 

 British species has been consigned to it : as to Ne&ra and 

 Poromya, newly constituted genera, our reasons for intro- 

 ducing them to this family will appear hereafter. 



The Anatinidce have some connections with Corbula and 

 Pandora, but the greater length, separation, and slenderness 

 of the siphons still remind us of the vicinity of the TeUinidce. 

 A malacological character of high importance is attached to 

 this group, which we consider decisive of the propriety of 

 merging in Anatina the Lyonsia or Osteodesma, and the 

 Thracia and Cochleodesma of authors, which is,, that all the 

 British members of these genera have only a single branchial 

 lamina on each side. Two or three of the TelHnce have a 

 similar structure, but they are mere exceptions to a rule, and 

 evidence the point of passage between the Anatinae and Tellince ; 

 but in Anatina it is, we believe, the rule ; though we cannot 

 positively assert that it applies to Neasra and Poromya, yet 

 there is little doubt that it does ; but as the species are not 

 uncommon in Scotland, we hope that the Northmen will 

 enlighten us on this point. 



ANATINA, Lamarck. 



Thracia, Receutiorum. 



A. PHASEOLINA, Lamarck et nobis. 



Thracia phaseolina, Brit. Moll. i. p. 221, pi. 17. f. 5, 6; (animal) 

 pi. H. f.4. 



Animal subovally elongated, moderately thick, pale brown ; 

 mantle closed, except a fissure quite anteriorly for the passage 

 of a compressed, not very long, spatulate foot, with a rounded 

 extremity, and posteriorly, for the issue of two moderately 

 long siphons, which are separate nearly their length, but the 

 animal always carries them in a divergent posture at the 

 extremities; both are furnished at the orifice with a few 

 minute rays ; the tubes are capable of great inflation. There 

 is only one large, suboval, pale brown branchial lamina on 

 each side, smooth within and pectinated without ; each lamina 



