42 



side, the umbones situated in about the anterior third of the length, and the sculpture consisting 

 of fine radiating striae, which are developed into widely placed, thick and irregular ridges on die 

 posterior slope behind the umbones. 



Distribution : — - The species was described from the Philippines and Lamv has recorded 

 it from New Caledonia and Madag^ascar. 



In the "Siboga" collection it is represented by 3 young shells fi-om Taruna Bay, Great 

 Sangir Island (St. 127), and a half grown spécimen from Fau-Anchorage, West Coast of Gebe 

 Island (St. 149). 



2. Arca [Bardaiia) decussata Sowerby. 



1819. Arca trapezina Lamarck (ex parte), Anim. sans Vertèb., VI, p. 41. 

 1833. Byssoarca decussata Sowerby (non Linn.), Proc. Zool. Soc. London, p. 18. 

 1841. Arca trapezina Delessert, Réc. Coq. Lamarck, pi. XI, fig. 13. 



1844. Arca decussata and A. trapezina Reeve, Conch. Icon., 11, Arca, pi. XII, fig. 81, pi. XV, fig. 103. 



1845. Arca decussata Catlow & Reeve, Conch. Nomencl., p. 49. 

 1848. Arca decussata Nyst, Mém. Acad. Roy. Belgique, XII, p. 24. 

 1853. Arca stigmosa Dunker, Ind. Moll. Guin., p. 46, pi. XI, figs. 8 — 10. 



1857. ^^l'Cd [Barbatia) decussata Adams, H. & A., Gen. Rec. Moll., II, p. 534. 



1858. Arca [Byssoarca) decussata Fischer, P., Journ. ConchylioL, VII, p. 339. 

 1860. Arca decussata and A. trapezina Reeve, Elem. Conch., II, p. 93. 

 1863. Arca decussata Deshayes, Moll. Réunion, p. 22. 



1865. Arca decussata Fraser, Proc. Zool. Soc. London, p. 196. 



1867. Arca decussata Mitchell, Cat. Mus. Madras, p. 73. 



1869. Arca [Byssoarca) decussata Lischke, Japan. Meeresconch., I, p. 14g. 



1869. Barbatia decussata Frauenfeld, Abhandl. Zool. -Bot. Ges. "VVien, XIX, p. 886. 



1869. Barbatia decussata Dunker, Cat. Mus. Godeffroy, IV, p. 114. 



1870. Barbatia decussata and B. trapezina Mac Andrew, Ann. Mag. Nat. Hist., (4), VI, p. 449. 

 1870. Arca decïLSsata Fischer, P., Journ. ConchylioL, XVIII, p. 170. 



1870. Barbatia oblonga and B.petcrsi Dunker, Novitat., Conch., Moll. Mar., p. 107, pi. XXXVIII, 



figs. 4—7, p. 135. pl- XLV, figs. 5—7. 



1871. Arca decitssata Lischke, Japan. Meeresconch., H, p. 142. 



1871. Arca decussata Von Martens & Langkavel, Donum Bismarckianum, pp. 55, 57. 

 1874. Arca decussata Lischke, Japan. Meeresconch., III, p. 107. 

 1874. Barbatia decussata Dunker, Cat. Mus. Godeffroy, V, p. 174. 



1876. Arca decussata Tapparone-Canefri, Viag. "Magenta", p. 242. 



1877. Arca [Barbatia) decussata Pagenstecher, Zool. Ergebn. Reise, Rothenmeer. Mollusk, p. 35. 

 1880. Arca [Barbatia) stigmosa Dohrn, Jahrb. Deutsch. Malakozool. Ges., VII, p. 173. 



1880. Arca [Barbatia) decussata and A. [B.) trapezina von Martens, Mobius Beitràg. Meeresf. 



Mauritius, Seychell., p. 320. 



1881. Barbatia decussata de Rochebrune, Bull. Soc. Philomat. Paris, (7) V, p. 5. 



1882. Barbatia decussata Dunker, Ind. Moll. Mar. Japon., p. 232. 



1886. Arca decussata Cooke, Ann. Mag. Nat. Hist. (5) XVIII, p. 93. 



1887. Arca decussata Von Martens, Journ. Linn. Soc. London (Zool.), XXI, p. 207. 



1887. Arca decussata Cheeseman, Trans. N. Z. Inst., VIII, p. 175. 



1888. Barbatia oblonga Jousseaume, Mém. Soc. Zool. France, I, p. 213. 



1890. Barbatia decussata, B. oblonga^ B. pctersi, B. stigmosa and B. trapezina Paetel, Cat. 

 Conch. Samm., III, pp. 213, 214. 



1890. Arca [Barbatia) decussata Kobelt in Martini, Chemn. Conch. -Cab., (N. F.) VIII (2), Arca^ 



p. 144, pl. XXXVII, figs. 2, 3. 



1891. Arca [Barbatia) petersi, A. [B.) stigmosa and A. [B.) trapezina Kobelt, Op. cit., p. 182, 



pl. XLV, figs. I, 2; p. 208, pl. XLIX, figs. 4, 5; p. 230, pl. XLVII, fig. 9. 

 1891. Arca [Barbatia) decussata Fischer, P., Bull. Soc. Nat. Hist. d'Autun, IV, p. 215. 



