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Show 134 MR. 0. W. ANDREWS AND OTHERS ON THE [Feb. 20, only the inner third, where they are divided into two zones by a shallow space. Spicules. Megascleres-strongyloxea, 1330 x 35 p. Microscleres-spherasters, 60 p. Somal chiasters, 15-18/x. Dermal chiasters, 12 p. The unique specimen measures 2*5 x 2 c.c. in horizontal and 2-5 c.c. in vertical plane. The rough convex under surface appears to have been torn off from a rock. The name given to the species denotes its close affinity to T.japonica Sollas; it differs from the latter (1) in its mode of growth, T. japonica being spherical and free, (2) in having the membranous oscular cones, and (3) in the slight difference in size between the dermal and somal chiasters. SPIRASTRELLA CARNOSA Topsent. 1897. Spirastrella carnosa Topsent (18. p. 441). The specimen is cauliflower-shaped, expanding upwards from a narrow base to a height of 2 c.c, the area of the upper surface being 2*5 x 1*5 c.c. The upper surface is covered with low rounded papillae. The tylostyles, 525 x 18 p, usually have a trilobate head. The spirasters are extremely rare and very fine, being 1 8 x 1 p, with minute spines, and usually with four curves. The specimen differs from the type from Amboina in having larger megascleres, these being only 330 x 6 to 8 p in the latter. In Topsent's specimens, too, the surface is ridged (" fronce " ). Distribution. Amboina ; Christmas Island. SPIRASTRELLA DECTJMBENS Ridley, var. ROBUSTA, var. nov. 1887. Spirastrella decumbens var., Ridley and Dendy (13. p. 229, pi. xiv. fig. 12). 1898. Spirastrella semilunaris Lindgren (10. p. 323, pi. xix. fig. 23). There are two specimens of this variety-one (1) forming a thin yellow crust on a shell, the other (2) in the form of small fleshy lobes growing on Sidonops picteti. Specimen (1) has a shallow patent oscule 1*5 m m . in diameter; the surface shows a delicate reticulate pattern formed by the pore-areas, the pores being circular and 40 p in diameter ; sieve-like groups of 5 to 10 pores lead into subdermal spaces. A cavernous cortex from *5 to 1 m m . in thickness occurs in the type specimens of the species from Torres Straits, described bv Ridley (11. p. 470, pi. xliii. fig. c). The same structure is also present in the specimens from Amboina and Christinas Island. In all these specimens the minute semilunar spirasters (12^ in length) form the outermost dermal layer. Hence I have no doubt that Lindgren's species is a synonym : at the same time it is right to add that that author is in no way to blame, owing to the incomplete description of the type specimens, which are badly preserved. |