JUKES-BROWNE : ON DOSINIA LUCINALIS (lAMK.). 215 



Moreover, Mr. Smith found that there was another shell in the 

 Museum Collection which agreed in everj' essential respect with 

 the lucinalis and striatissima ; this was a shell in Cuming's collection 

 Avhich had been described by Iliimcr under the name oi D. amethystina} 

 There is a full description of this shell in Homer's monograph of 

 Dosinia {Novitates Conch., Abt. ii, Suppl., p. 80, Cassel, 1862), but 

 he never figured it. The description might be one of lucinalis or 

 striatissima, except that, instead of being white, it is described as 

 " violascente albida, ad umbonum regionem amethystina ", and also 

 that the pallial sinus is rounded at the end. Mr. Smith, however, 

 is of opinion that these are merely varietal charactei's, and that the 

 shell described by Romer is undoubtedly a variety of D. lucinalis. 



Thus the identification of my shell with the types of lucinalis., 

 striatissima, and amethystina becomes a matter of some importance, 

 because it not only establishes the identity of three species which 

 were supposed to be different, but shows that Lamarck's shell was 

 not the unique specimen that Romer imagined it to be, and also 

 reveals the fact that it is a form which varies much in colour. 



Under these circumstances it seems desirable to give a more complete 

 description of B. lucinalis than has yet been published, and I think 

 the following will be found to include all the characters which are 

 of any real importance. 



Dosinia lucinalis (Lamk.). 



Testa solida, ad figuram fere circulari, alt. 24-8, lat. 24-8 mm., 

 sub-convexa, insequilaterali ; umbonibus parvis, obtusis, incurvatis ; 

 lineis elevatis, tenuibus, confeitis, subtiliter nodulatis, ex umbonibus 

 radiantibus ornata, et liris concentricis, erectis, distantibus cincta; 

 lunula lanceolata, valde impressa, in medio prominente ; area 

 posteriori lanceolata, marginibus angulatis limitata, medio in alse 

 formam labiis prominentibus surrecta, inter et subter quae ligamentum 

 vix conspicuum videtur. 



Colore variabili, interdum omnino alba, interdum in parte vetustiori 

 colore melino, vel amethystino, vel rubido tincta. Pagina interna 

 alba, vel amethystina, vel rubida ; sinu palliari profundo, ascendente, 

 in extremitate anteriori rotundato vel obtuse angulari ; lamina 

 cardinali valida, latissima, dente lateral! in valva dextra, papilliformi, 

 rugoso ; dente cardinali mediano crasso, rugoso ; dentibus in valva 

 sinistra normalibus. Valva dextra margins posteriori strige vel sulco 

 angusto, brevi sed profundo, inciso. 



Shell solid, nearly circular in outline, measuring from 24 to 28 mm. 

 both in height and in width ; moderately convex, inequilateral, 

 with small, obtuse, incurved umbones ; ornamented with numerous 

 fine raised lines or riblets, which radiate from the umbones, and are 

 crossed by less numerous concentric ridges or lamellae, as well as by 

 fine striae, which give them a wavy or nodulated appearance. Lunule 

 lanceolate, deeply impressed, with pouting lips ; escutcheon rather 

 narrow, defined by angular inflexions, and rising along the median 



^ Proc. Zool. See. Lend., 1860, p. 118. 

 VOL. X. — OCTOBEK, 1912. 15 



