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Show 1903.] FROM ZANZIBAR AND BRITISH EAST AFRICA. 107 been studied only in a few cases. Consequently it cannot, unfortunately, be employed as one of the principal characters in sub-dividing the genus. I give below a tentative table of the species of the genus hitherto described, with their distribution :- A. Species with eyes on the anterior part of the margin only. a. Ovaries dorsal. S. pilidium (Gotte) [1]. [Mediterranean. Valpa- /3. Ovaries ventral. raiso(v. Plehn) [4]. Marginal eyes extremely small. S. neapolitanus (Delle Chiaje) [1]. Mediterranean. Marginal eyes moderate, brain-eyes absent ? S. zanzibaricus, sp. nov. Zanzibar. y. Position of ovaries doubtful. S. frontalis Verrill [2]. New England. S. Umosus Diesing [1]. Japan. S. conglomeratus Diesing [1]. Japan. B. Species with eyes completely surrounding the margin. a. Ovaries dorsal. Small brightly coloured species. S. plessisii Lang [1]. Mediterranean. b. Ovaries ventral. S. suesensis Ehrenb. ? [1]. Zanzibar. c. Position of ovaries doubtful. S. suesensis Ehrenb. [1]. Red Sea. S. argus Czerniowsky [1]. Black Sea. S. ? zebra Verrill [2]. New England. Since the publication of Lang's Monograph, the following-species have been removed from the genus:- 1. Stylochus littoralis (Verrill) = Planocera, elliptica Girard. This species is now referred by Verrill to a new genus, Eustylo-chus, characterised by the presence of a median female anterior accessory vesicle, apparently similar to that found in Paraplanocera. 2. Stylochus^ sargassicola (Mertens) is referred by von Graff to the genus Stylochoplana [3]. Verrill's species Stylochus crassus [2] is, I think, evidently not a member of this genus. Family LEPTOPLANID^E. PHYLLOPLANA LACTEA, gen. et sp. nov. (Plate IX. fig. 3.) Shore form. " White, with minute grey dots scattered sparsely over dorsal surface." Collected 19.2.01 ; several specimens. |