elongated in an antero-posterior direction. The umbones also are more curved forvvards, downwards 

 and later upwards; the posterior ridge limiting the escutcheon is sharper and the ribbing doser. 



Distribution: — /. [M.) vulgaris appears to be the common Indo-Pacific species of the genus. 



The "Siboga" Expédition obtained a fevv dead valves in a trawl in the Madura Strait 

 (St. 2, 56 mètres). 



3. Isocardia [Meiocardia^ lamarcki Reeve. 



1792. Cardita Moltkiana Bruguière (non Spengler), Encyclopéd. Méthod., p. 404. 



1797. Bruguière, Encyclopéd Méthod., pi. CCXXXIII, figs. \a — d. 



1801. Isocardia Moltkiana Lamarck, Syst. Anim. sans Vertèb., p. 118. 



1805. Isocardia Moltkiana De Roissy in Bufifon, Hist. Nat. Moll., VI, p. 384. 



181 7. Chania Moltkiana Dillwyn, Descr. Cat., I, p. 213. 



18 19. Isocardia Moltkiana Lamarck, Anim. sans Vertèb., VI, p. 31. 



1822. Isocardia Moltkiana Blainville, Dict. Sci. Nat., XXIV, p. 17. 



1825. Isocardia Moltkiana Sovverby, Cat. Tankerville, p. 18. 



1825. Chania Moltkiana Wood, Ind. Test., p. 42, pi. IX, fig. 5. 



1830. Isocardia Moltkiana Deshayes, Encyclopéd. Méthod., II, p. 322. 



1835. Isocardia Moltkiana Deshayes in Lamarck, Anim. sans Vertèb., VI, p. 447. 



1841. Isocardia Moltkiana Reeve, Conch. Syst., I, p. lOi, pi. LXXVIII, fig. 2. 



1843. Chama Moltkiana Hanley, Rec. Biv. Shells, p. 150. 



1845. Isocardia Lainarckii Reeve, Conch. Icon., II, Isocardia, pi. I, fig. 5. 



1845. Isocardia Lainarckii Catlow & Reeve, Conch. Nomencl., p. 45. 



1853. Isocardia Lainarckii Môrch, Cat. Yoldi, II, p. 38. 



1856. Isocardia Laniarckii Hanley, Rec. Biv. Shells, Appendix, p. 370, pi. XVIII, fig. 3, 4. 



1857. Bucardia [Meiocardia) Laniarckii Adams, H. & A., Gen. Rec. Moll., II, p. 461. 

 1860. Isocardia Laniarckii Reeve, Elem. Conch., II, p. 104. 



1868. Isocardia [Meiocardia] vnlgaris var. Laniarckii, Rômer in Martini-Chemn. Conch. -Cab. 



(N. F.), X (2), Cardiacea, p. 9. 

 1878. Isocardia [Meiocardia] Laniarckiana Kobelt, lUustr. Conchylienbuch, p. 347. 

 1884. Isocardia Laniarckii Grasset, Ind. Test. Viv., p. 273. 



1890. Isocardia [ISIeiocardia] vnlgaris var. Lamarcki Paetel, Cat. Conch. Samm., III, p. 120. 

 1903. Meiocardia laniarckii Smith, Faun, Geogr. Maldive, Laccadive Archipel., II, p. 625. 

 1906. Isocardia [Meiocardia] laniarckii Melvill & Standen, Proc. Zool. Soc. London, p. 814. 

 1906. Isocardia lamarcki Standen & Leicester, Ceylon Pearl Oyster Rept., V, p. 292. 

 191 1. Isocardia lamarcki Lamy, Bull. Mus. d'Hist. Nat. Paris, XVII, p. 132. 

 191 1. Isocardia lamarcki Pelseneer, "Siboga" Lamellibranches (Anat.), pi. XVIII, fig. i. 

 1920. Isocardia [Meiocardia] Moltkiana var. Lamarcki Lamy, Journ. Conchyliol., LXIV, p. 298. 



The distinguishing characters of /. (vl/.) lamarcki from /. i^M?) vulgaris hâve been 

 discussed under the latter species. It is, however, possible that with more material it may hâve 

 to be regarded as a variety of /. {M.^ vulgaris. 



Distribution: — - The range of /. {M.) lamarcki is similar to that of /. [M^i vttlgaris. 



The "Siboga" Expédition dredged a few young valves of this species in the western 

 entrance of the Samau Strait (St. 59, 390 mètres). 



4. Isocardia [Meiocardia^ tetragona Adams & Reeve. (Plate V, figs. 3, 4). 



1850. Isocardia tetragona Adams & Reeve, "Samarang" Moll., p. 'jd, pi. XXII, fig. i. 

 1857. Isocardia [Meiocardia) tetragona Adams, H. & A., Gen. Rec. Moll., II, p. 461. 

 1860. Isocardia tetragona Reeve, Elem. Conch., II, p. 104. 



