LAMELUBRANCHIATA. jq 



The contour changes from the obliquely cordifonn or quite triangular (see PI. Ill, fig.oi; just 

 as in C. exiguum) to become broadly oval or almost circular. 



There is also great variation in regard to the sculpture. Sometimes for example, the ribs ma\ 

 be rough with scales and pointed tubercles not only on the anterior and posterior area, but the 

 middle area may also be partially or wholly beset with scales or tubercles; in this way we obtain a 

 form such as that figured in PI. Ill, fig. o,e, the sculpture of which resembles that in ' •im, but 



transitions show, that it can be traced back to the common form C.fasciatum with smooth, central 

 ribs. In the young, with contour like that of C. exiguum, the posterior ribs are beset with ver\ 

 pointed and comparatively long spines. 



The ribs are usually quite flat and only separated by a fine line, but very often the interspace 

 between them is somewhat broader, yet never so broad as the ribs themselves. Sometimes, however, 

 the ribs are more or less convex, especially when they are separated by a distinct interspace. Not 

 rarely an intercostal sculpture is seen under the lens in the form of a fine pricking (PI. Ill, fig. 9k). 



I have further represented (PI. Ill, fig. 91, g and h) that form of C.fasciatum, which was con- 

 fused by Morch with C.edule; the resemblance is striking, indeed, but the pointed tubercles on the 

 posterior ribs (PI. Ill, fig. gh) reveal its true nature - - in C. cdule the rugosities are laniellifonn here. 



Cardium nodosum Turton. 



[Faeroes]. 

 To this species Morch (Vidensk. Medd. Naturh. Foren. Kbhvn. 1867, p. 04) refers 7 specimens 

 from Thorshavn in the Faeroes. I have not been able to find these specimens here in the Museum, 

 and as the species is not present in the considerable collections, which have been made at the Fseroes 

 in recent years, I think it very doubtful, if the species occurs there. Possibly, an unusually well 

 sculptured form of C.fasciatum (cf. above and PL III, fig. ge) has given rise to the confusion. 



Cardium ciliatum Fabricius. 



PI. Ill, fig. 10 (young). 

 Cardium ciliatum Fabricius, Fauna groenl., 1780, p. 410. - Cardium islandicum Chemnitz, Conch. 



Cab. VI, 17S2, p. 200, PI. 19, fig. 195 — 96. l ) — Cardium pubcsccns Con thou y, Boston Join 11. Xal. 



Hist. II, 1838, p. 60, PL 3, fig. 6 — Cardium arcticum Sowerby, Proc. Zool. Soc. 1840, p. mi'; 



Conch. Illustr., 1841, fig. 26. - Cardium Haye sii S t i m p s o u, Proc. Acad. Nat. Sc. Philadelphia, 



1S63, p. 58; Packard, Mem. Boston Soc. Nat. Hist. 1, 1867, p. 278, PL 7, fig. 14. dium 



islandicum Could & Binney, Rep. Invert. Mass., 1870, p. 130. fig- 15 a Cardium ciliatum 



Sars, Moll. Reg. Arct. Norv., 1878, p. 46, PL 5, tig. 4. 

 Cardium edule Mohr (11011 Liune), Forsog til en Islandsk Naturhistorie, 1786, p 1 



islandicum Moller, Index Moll. Groenl., 1842, p. 20. Cardium ciliatum Morch, Rink's 



the material collected from Denmark; it is only among the specimens from the Kattegat thai there arc some which resemble 

 the ventricose, keeled form from Iceland and the l'aji'"es. 



>) Chemnitz is the author of the name Cardium islandicum, not I.inne, as tin species first occurs in the i;lli Ed. 

 of Syst. Nat, pars 6, i/y2 (p. 3252 J and with a reference to Chemnitz' work ol 1 •' B\ erroneo the 1 



C.islandicum to the 12th Ed (1767 of l.innei Syst. Nat. (though 110 Cardium of that name occurs thei ' oldei authors 



have got the present species renamed "Cardium islandicum I, inn."; t hi-- erroi appears again ill KobeU's Prodr. Faun. Moll. 

 Test. Mar. Eur. (1SS0). 



