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Clams
Clams The difference between the Seychelles (mean 4.3), East Africa (5.0) and South Africa (7.7) is obvious. Therefore there is not only a local tendency of variation, but also a regional one: one is justified to summarize adjacent localities and to calculate an average class of marking in each region:
Kowie-Pondo 7.9, Natal 7.3, Mozambique 6.5, East Africa 5.0,
Madagascar 6.5, Mascarenes 5.1, Seychelles 4.3, Gulf of Aden 6.3,
Ceylon 5.8, West Sumatra 5.6, South Java 6.1, N. W. Australia 4.9,
S. W. Australia 5.7, East Australia 6.0, New Caledonia 4.5, Fiji-Samoa 4.8,
Solomon Is. 5.2, Bismarck Arch. 5.6, Moluccas 5.1, Java Sea 5.8,
Philippines 5.6, Taiwan-Japan 5.6, Bonin-Guam 6.0, Caroline Is. 4.2,
Marshall Is. 3.9, Gilbert Is. 3.7, Tabiti-Tuamotu 4.0, Line Is. 3.4,
Philippine Is. 3.7, Midway Is. 4.6.
The mean of these 30 regions is class 5.3 (dotted area very slightly exceeding the speckled one). If one replaces the five intervals 3.4-4.3, 4.4-5.3, 5.4-6.3, 6.4-7.3, 7.4-7.9 by visual signs and plots them into a map, one will observe great geographical tendencies: 1. in the centers of oceans, especially from the Tuamotu Is. to Philippines and Micronesia, and in a smaller area around the Seychelles, the brown dots are least developed; 2. they pass into the subcontinental regions from Japan to Australia and Ceylon as well as along the East coast of Africa, in which the brown dots slightly exceed the white specks; 3. in South Africa there is a center of maximum development of brown dots, which character fades in the adjacent regions of Mozambique and Madagascar.
This study on the dorsal markings of E. helvola shows that careful registration of such superficial and variable characters bring to light interesting ways of geographical evolution.
Clams Based on known locality characteristics there are only a very few additional places where C. teulerei may someday be collected. In the Red Sea the following areas should produce specimens: the extensive coral reef formations bordering the coast of Africa for 120 miles south from Port Sudan (1); the extensive fringe and barrier reef area known as Dahlec Banks (6) also off the African Coast in the Red Sea; still in the Red Sea but off the coast of the Arabian, Peninsula is Farasan Island (7) and an extensive barrier reef system stretching 360 miles south from Iith to within about 100 miles of Mocha (it is from this area the specimens labeled "Mocha"' probably came). In the Arabian Sea the only area other than Al Masirah with similar restrictive characteristics is that found at a group of small islands in Kuria Muria Bay (8) (some 200 miles south-west of Al Masirah) where a system of barrier and fringing reefs exist.
In résumé, it seems collectors, if and when they visit the Red Sea-Arabian Sea-Persian Gulf area, should look for clean sand areas in shallow water with plenty of fringing and barrier coral reefs that are well removed from the surrounding deep water and protected from the open sea. Warm water, moderate salinity, and little if any fresh water run off are also probably important considerations.
Another research paper received recently that will be of interest to Indo-Pacific collectors is THE LITTORAL MARINE MOLLUSKS OF COCOS-KEELING ISLANDS (Indian Ocean), by Virginia Orr Maes of the Academy of Natural Sciences of Philadelphia. This paper, of over 100 pages, is part of the Proceedings of the Academy of Natural Science of Philadelphia, Vol. 119, No. 4, 1967. It is available as a paper-back reprint.
The Cocos-Keelings are a small group of low-lying islands in the eastern Indian Ocean. A total of 504 species of shells have been collected or attributed to this group. Of the 379 forms identified by the author, 82 percent are widespread Indo-Pacific in distribution, many of them found in Philippine waters. The paper discussed gives an annotated list of mollusks and includes the habitat notes for most species. Also observation on feeding, commensalism, radulae, and colors of soft parts of living animals are noted for many species. Twenty-five pages of black and white photographs illustrate most of the shells and will provide collectors with photographs of many shells collected in Philippines, not otherwise pictured in readily available literature.
Copies of this work are available from The Department of Mollusks, The Academy of Natural Sciences of Philadelphia, 19th and Parkway, Philadelphia, Pa. 19103. Price of the illustrated, 124 page reprint is $2.50.
The sea shell Blasicrura coxeni Cox shows the tendency to develop geographical races and local variants though the species is restricted to western Melanesia. The coarsely spotted race B. hesperina Schilder & Summers from New Britain is well separable from the finely speckled B. coxeni from the Solomon Is.; the B. coxeni from Astrolabe Bay figured by Schilder in 1928 (Arch. Moll. 60:193) may constitute a further local variant, as well as B. steineri Cate 1969 from the Russel Is. in the Solomon Is. Besides, W. O. Cernohorsky figured a curious variant from the New Hebrides in which the interstices of teeth become orange (illustrated & described in Sean Raynon Sabado: 107:8, November, 1968).
Recently Mr. A. Kalnins (Maylands, West Australia) sent me two B. coxeni collected alive by fishermen "on one of the islands near New Caledonia" in 1965. Both shells are finely though closely speckled like B. coxeni from the Solomon Is., their margins are very callous with the cream-colored callus extending far towards the dorsum; also they exhibit four blackish brown spots varying from the usual size of the terminal spots of B. quadrimaculata Gray to enormous extent, thus proving the close relationship of the two species.
The left figure represents the shell kindly presented by Mr. Kalnins to the writer (coll. Schilder 23426), the right shell will be deposited in the Museum of Perth.
If the orange interstices of teeth in other shells from the New Hebrides should be constant, the local race should be named, as well as the new four-spotted variant, when its exact habitat should become known.
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