120 oA 
Arca (Anadara) uropygomelana, Bory. 
Arca uropigimelana, Bory dE St Vincent, Encyclopédie méthod., 1797, pl. 307, fig. 2. 
(Anomalocardia) uropygmelana, Bory, MArrint u. CHEMNITZ, Conchyl. Cabin., VIII, 2 Abth., p. 85, 
pl. 23, figs. 5—6. 
— (Anadara) er Bory DE Saint-VINCENT, Lamy, Bull. du Mus. d’Hist. Nat. Paris, 1904, p. 277. 
= = — Journ. de Conchyl., vol. 55, 1907, p. 207. 
- haloeentees REEveE, Proc. Zool. Soc. ander XII, 1844, p. 39. 
— -- — Conchol. icon., II, Area, Sp. 11. 
_ — = Morcer, Journ. de Conchyl., vol. 37, 1889, p. 162. 
(Anadara) holosericea, Reryr, P. FiscHer, Catal. de Moll. de l'Indo-Chine, p. 216. 
— — holoserica, — Epa. SmirH, Proc. Zool. Soc. London, 1891, p. 431. 
Mor-et (loc. cit.) states that the present species (A. holoserica, Reeve) is taken 
at “Isles du golfe de Siam.” Lamy, however, points out (Journ. de Conchyl., vol. 
55, 1907, p. 242) that this statement is due to erroneous determination by Mor vet, 
and that the specimens belong to Arca cornea, Reeve var. Cecillet (Phil.), Lamy 
(compare this species). Nor did the Danish Expedition to Siam collect any specimens 
of A. uropygomelana, Bory (= A. holoserica, Reeve). 
Distribution: — Salanga (Malacca), Felidu Atoll and Hulule Isl. (Maldive 
Archip.), Gulf of Aden, Red Sea, Mauritius, Madagascar, Seychelles, East Africa, 
Querimba Isls. — Philippines, Java, Togean Isls., Moluccas, Gilbert Isls. (Kingsmill), 
New Caledonia. 
Srurany! states that a specimen (of A. scapha, Chemn.) resembling A. holo- 
serica, Reeve, has been taken at Ras Abu Somer (Red Sea). W. J. Hart and 
R. STANDEN state* that A. uropygomelana, Bory, has been taken on “a raised coral 
reef” at Port Sudan, near Suakim, on the west coast of the Red Sea. Lastly, Lamy 
states® that specimens from the Red Sea are in the Paris Museum. 
Arca (Anadara) Mortenseni, n. sp. 
(Pl. Il, Figs. 1—2). 
This shell is oval, thin, and rather ventricose. The front passes evenly 
and with rounded outline into the ventral side, while the hinder part is more 
straightly truncate, and forms a rounded angle with the ventral part. It is white, 
and bears about 47 sharp radiating ribs which are closely covered with small, 
regularly-arranged nodules and scales, crossed by fine, concentric lines of growth 
which give the surface a beautiful, reticulated appearance. Not all the radiating 
ribs extend over the umbones, but many unite with an adjacent rib. The inter- 
stices between the ribs are generally narrower than the ribs, and are finely sculp- 
tured. A keel, upon which the radiating ribs are further apart and stouter than 
are the other ribs, extends from the umbones towards the posterior part of the 
ventral side. Owing to this keel, the well-raised, prominent umbones become oblique, 
and are higher towards the hinder part. The umbones are situated at about the 
middle of the shell, a trifle nearer its anterior end. The ligament-area is small 
and narrow. There are about 25—26 hinge-teeth, divergent on each side of the 
centre. The interior is white; the exterior ribs are there slightly noticeable, and 
' Lamellibranchiaten d. Rothen Meeres, 1899, p. 36. 
* Journal of Conchology, vol. 12, 1907, p. 68. 
' loe. cit., Journ. de Conchyl., 1907, p. 209. 
