78 ARCADE. 



mixed up with a flake- white ovary; but from the extreme 

 tenderness of the branchiae, I cannot speak of them and the 

 palpi with certainty as to form and number. 



July, 1852. As I had just finished the above, a lively 

 specimen of this species was met with, which, on being placed 

 in water, at once unfurled its long and beautiful fringes, and 

 exserted the ample niveous mantle and foot. This is certainly 

 the Prince of British bivalves ; the snow-white colour of both 

 animal and shell sheds over this interesting creature the in- 

 expressible charms of purity and elegance. It now lives in 

 the same vase with its pigmy congener, the L. convexum. 



L. CLARKITE (nova species), Clark. 

 L. Clarkia, Brit. Moll. iv. p. 255, pi. 132. f. 7- 



L. testa fragili, obliquo-subovali, compressa, postice et antice rotuudata, 

 albida, mediocriter nitida, striis concentricis, confertis, tenuibus 

 notata; apices minutos, prominulos, subtilissime punctatos gerente. 

 Latus rostris anterius, quoad longitudinem transversam, duplo 

 posterius superat. In valva dextra, utroque, dentes laterales, 

 duplices, distantes apparent ; in sinistra, simplices ; inter quos, utra- 

 que valva, dens unicus, primarius, erectus, acutus, oritur. 



Mensura obliqua -TJ-, transversa y^, altitude aut crassitude ^ uncise. 



Zonam corallinam Devoniae meridionalis, prope ostium Iscae, rarius 

 habitat. 



Animal ignotum. 



Of this minute and elegant species, a series of eighteen 

 perfect specimens have occurred, and having compared the 

 hinge and dentition with forty examples of the L. convexum 

 and L. nitidum, I can state that there is not the slightest 

 variation in this respect in the three species. Its distinguish- 

 ing characters are the almost perfect obliquely oval shape, 

 being without a trace of the subangularity which is invariably 

 seen at both extremities of the congeneric Leptons; and, as 

 to the punctures, it is more devoid of them than the glabrous 

 varieties of the L. nitidum, which, however, in the forty spe- 

 cimens I possess, all show more or less the punctured aspect 

 on the umbonal area ; but in the L. Clarkia only the apical 

 circumscribed space is in some, but not in all examples, almost 



