96 



A number of species of this subgenus described by Reeve and Dunker appear, from the 

 very little différences in the shells, to be only local forms. Unfortunately, however, very little 

 material of this subg-enus is available, and it is not possible therefore, to understand the range 

 of variation of the varions species. 



The génotype, according to Stoliczka, is P. [E.) smaragdina (Reeve). 



I. Pteria [Electromd) ala corvi (Dillwyn). 



1785. Ala corvi pendilla etc., Chemnitz, Conch.-Cab., VIII, p. 144, pi. LXXXI, fig. 727. 



1790. Mytiliis hirundo var. y Gmelin (non Linn.), Syst. Nat. (éd. XIII), p. 3357. 



1817. Mytilns ala-corvi Dillwyn, Descr. Cat., I, p. 322. 



1825. Mytilns Ala-corvi Wood, Ind. Test., p. 59, pi. XII, fig. 44. 



1830. Avicula lingnattda Deshayes, Encyclopéd. Méthod., III, p. 104. 



1836. Avicula Imguatida Deshayes in Lamarck, Anim. sans Vertèb., VII, p. 103. 



1840. "i Avicula costellata Ffeiffer, Krit. Reg., p. 'j6. 



1843. Avicula Ala-corvi Hanley, Rec. Biv. Shells, p. 263. 



1845. Avicula alacorvi Catlovv & Reeve, Conch. Nomencl., p. 78. 



1853. Margaritifera semiaurita Morch, Cat. Yoldi, II, p. 50. 



1856. Mytdus ala-corvi Hanley in Wood, Ind. Test., p. 70, pi. XII, fig. 44. 



1857. Avicula ala-corvi Reeve, Conch. Icon., X, Avicula, pi. XII, figs. 44^, b. 

 1857. Avicula linguatula Adams, H. & A., Gen. Rec. Moll., II, p. 525. 

 1860. Avicula ala-corvi Reeve, Elem. Conch., II, p. 63. 



1869. Avicula ala corvi Issel, Malacol. Mar. Rosso, p. 95. 



1870. Avicula ala corvi Mac Andrew, Ann. Mag. Nat. Hist., (4) VI, p. 448. 



1872. Avicula ala corvi Dunker in Martini-Chemn. Conch.-Cab. (N. F.), VII (3), Avicula, p. 34, 

 pi. X, fig. 7. 



1876. Avicula ala-corvi Tapparone Canefri, Viag. "Magenta", p. 251. 



1877. Avicula ala corvi Pagenstecher, Zool. Ergebn. Reise Rothenmeer. Moll., p. 33. 

 1880. Avicula ala-corvi von Martens, Mobius Beitràge Meeresf. Mauritius, Seychell., p. 316. 

 1884. Avicula ala-corvi Grasset, Ind. Test. Viv., p. 302. 



1886. Avicula ala-corvi Cooke, Ann. Mag. Nat. Hist., (5) XVII, p. 136. 



1890. Avicula ala-corvi Paetel, Cat. Conch. Samm., III, p. 202. 



1893. Avicula ala-corvi Dautzenberg, Bull. Soc. ZooL France, XVII, p. 84. 



1898. Avicula ala-corvi Melvill & Standen, Journ. Linn. Soc. London (ZooL), XXVII, p. 183. 



1901. Avicula ala-corvi Sturany, Denkschr. Kais. Akad. Wiss. Wien (Math. -Nat.), LXIX, p. 288. 



1906. Electronia ala-corvi Smith, Fauna Geogr. Maldive and Laccadive Archipel., II, p. 623. 



1909. Pteria ala-corvi Melvill, Trans. Linn. Soc. London (ZooL), XIII, p. 124. 



1910. Pteria alacorvi Hedley, Austral. Ass. Adv. Sci., XII, p. 344. 



191 1. Avicula [Electroma) ala-corvi, Pelseneer, "Siboga" Lamellibranches (Anat.), p. 24. 



As has been noted in the account of the subgenus Electroma, the insufficient material 

 of the several species described by Reeve and others, makes it almost impossible to décide 

 definitely about the range of variation in shape and colour of the shells of the various species. 

 The older of the two shells, which I assign to this species, agrées in outline with spécimens of 

 P. (E.) a/a corvi from the Red Sea, but the spécimen is much lighter in colour. 



Distribution : - — P . [E.) ala corvi has been recorded from the Red Sea, the Laccadive 

 and Maldive Archipelagos and Australia. It appears to hâve a wide distribution in the Indo- 

 Pacific, and probably a number of the socalled species of Eleclro7na, described as new species 

 of Avicula by Dunker and Reeve, are based on local variations of this species. 



The "Siboga" Expédition shells, which I refer to this species, were obtained at Pulu 

 Kaniungan Ketjil (St. 89) and Banda Anchorage (St. 240). 



