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Show 308 MR. F. F. LAIDLAW OX THE [Apr. 21, (c) Prostate not chambered. 4. L. panamensis v. Plehn. Gulf of Panama [7]. 5. L. californica v. Plehn. California, Chatham Is. [11] 6. L. ncitionalis v. Plehn. Ascension Is. [8]. The following also belong to section A, but their position in the section cannot be determined without information as to the prostate characters. L. drcebachensis Oersted. Norway [6]. L.fcdlax (de Quatrefages) [6] should perhaps form a separate section of the genus on account of the great length of its stylet. It occurs on the south side of the English Channel. B. Penis unarmed. a. Prostate chambered. 7. L. chierchce von Plehn. Callao [7]. /3. Prostate not chambered. 8. L. pallida (de Quatrefages). Mediterranean [6]. 9. sp. (unnamed). Maldives [4]. y. No definite prostate. 10. L. pacificola von Plehn. Valparaiso [7]. 11. L. malayana, sp. n. Straits of Malacca. Belonging to this section but of uncertain position in it is L. angusta Verrill [13J from New England. L. lacteoalba Verrill [14] is insufficiently characterised, but said to be like L. pallida. S em o x ia p e x a x g e x s is , sp. n. Two specimens from Pulau Bidan. No note available as to colour. This interesting species agrees fairly closely with the only other species of the genus at present known, viz., S. macu-lata von Plehn, from Java [7]. It is, however, readily distinguished from that species by its external characters, the arrangement of the eye-spots being obviously very different and showing some approximation to the condition found in Discocelis tigrina (see text-fig. 53, p. 309). The dimensions of the larger specimen are as follows:- Total length, about ..........22 mm. Breadth, about .................11 „ Moutli-opening, about ... 9 „ from the hind end. Genital aperture ........... 1 ,, behind mouth-opening. Brain, about ................... 4 ,, from the anterior margin The marginal eyes extend back for about 8 mm. on either side. The arrangement of the brain and tentacle-eyes is shown in text-fig. 53, p. 309. An important distinction between this species and Semonia maculata is afforded by the fact that in the latter the testes and L. variabilis Giard. L. ellipsoides Verrill. L. virilis Verrill. |