29; 



;. Tridacna elongata Lamarck. 



1819. Tridacna elongata var. a Lamarck, Anim. sans Vertèb., VI, p. [06. 



183 1. Tridacna elongata Deshayes, Encyclopéd. Méthod., III, p, 1045. 



1836. Tridacna elongata var. a Deshayes in Lamarck, Anim. sans Vertèb., VII, p. 9. 



1843. Tridacna elongata Menke, Moll. Nov. Holland., p. 39. 



1845. Tridacna elongata Chenu, lUustr. Conchyliol., p. i, pi. I, fig. 2, pi. II, figs. i — 3. 



1869. Tridacna elongata Issel, Malacol. Mar. Rosso, p. 79. 



1884. Tridacna lanceolata Sowerby, Thés. Conch., V, p. 181, pi. CCCCLXXXIX, fig. 19. 



1889. Tridacna elongata Brazier, Mem. Austral. Mus., II, p. 28. 



1895. Tridacna elongata Pilsbry, Cat. Mar. Moll. Japan, p. 182. 



1903. Tridacna Reevei Hidalgo, Mem. Real Acad. Cienc, Madrid, XXI, p. 389. 



1906. Tridacna elongata Lamy, Bull. Mus. d'Hist. Nat. Paris, XII, p. 215. 



19 14. Tridacna elongata Iredale, Proc. Zool. Soc. London, p. 666. 



1914. Tridacna elongata Hedley, Proc. Geogr. Soc. S. Australia, VIII, p. 267. 



1921. Tridacna elongata Hedley, Mem. Austral. Mus., XIII, p. 167, pi. XXX, fig. 8. 



1928. Tridacna Reevei Faustino, Summary Philippine Mar. Freshw. Moll., p. 65. 



1930. Tridacna elongata Thiele, Faun. Siidwest Austral., V, p. 592. 



As Hedley has shown Lamarck confused with T. elongata at least three other species, 

 T. maxima Rôding, T. imbricata Roding and T. elongatissima Bianconi. The synonymy 

 given above is based on Hedley's work and I regard with Hedley the figures i, \a, i ^ on 

 Chenu's plate II (loc. cit.) as those of the typical form. T. elongata as figured by Reeve in 

 "Conch Icon". is T. vtaxima Roding. 



The shell is inequilateral, oblong and produced posteriorly ; the ventral margin is very 

 crenulate, and the seven convex ribs are covered with large foliaceous scales. In old shells the 

 ventral margins of the two valves in the central part do not meet in the middle, and a distinct 

 opening is left between the valves, even when fully closed. 



Distribution : — T. elongata has a wide range in the Indo-Pacific, and has also been 

 recorded from the Red Sea. 



In the "Siboga" collection the species is represented by shells from Lumu Lumu Shoal, 

 Bornéo Bank (St. 78), reef near ~ Anchorage off Beo, Karakelang Islands (St. 131), reef near 

 Anchorage off Lirung, Salibabu Islands (St. 133), reef near Anchorage south of Lucipara Group 

 (St. 225) and reef in Nalahia Bay, Nusa Laut Island (St. 234). 



Genus Hippopus Lamarck. 



1799. Hippopns Lamarck, Mém. Soc. Hist. Nat. Paris, p. 86. 



1857. Hippopns Adams, H. A., Gen. Rec. Moll., II, p. 465. 



1862. Hippopns Reeve, Conch. Icon., XIV, Hippopns^ pi. I (explanation). 



1868. Hippopus Kùster in Martini-Chemn., Conch. -Cab. (N. F.), VIII (4) Tridacna etc., p. 7. 



1887. Hippop7is Fischer, P., Man. Conchyliol., p. 1035. 



Good descriptions of the genus are published in the works cited above. The génotype 

 is Hippopus hippopzis (Linn.) — the only known species of the genus. 



I. Hippopus hippopus (Linn.). 



1685. Pectnnculiis major variegatiis Lister, Hist. Conch., pi. CCCXLIX. fig. 187; pi. CCCL, 



fig. 188. 

 1741. Chanta striata, Rumph, Amboin. Rarit., p. 131, pi. XLII, fig. c. 



