POLYCLAD TURBELLARIA. 135 



The arrangement of the ci/r-spotft is shown in fig. 6 on Plate. 



This species is a true Leptoplana belonging to the section of the genus* in which 

 the penis is not armed with a stylet. The prostate is chambered, with some five 

 compartments, it is small and of considerable length. 



L. gardineri is nearly related to L. chierchce, vox Plehn, from which it is readily 

 distinguished by the very different arrangement of the eye-spo.ts, by the greater 

 relative length of the prostate, and by the relatively small size of the accessory 

 vesicle of the vagina. 



Pseudoceros, sp. 



One specimen, referable to this genus, from the pearl banks, Gnlf of Manaar, is 

 unfortunately not in suitable condition for accurate description. It apparently 

 belongs to the section of the genus which is provided with only a single penis; the 

 colour is white with a fine black margin. The total length of the specimen is about 

 20 millims. 



Prosthiostonium singulare, n. sp. 



One specimen from Ceylon (Gardiner). 



Measurements. Length, about 40 millims. ; breadth, about G millims. Buccal 

 opening 6 millims. from the anterior end. Male aperture 16 millims. behind buccal 

 opening; female aperture 1*5 millims. behind male. Sucker 2 millims. behind female 

 aperture. 



The colour of the spirit specimen is uniform white. 



The marginal eye-spots are relatively very small and lie in an irregular row round 

 the front margin, extending back on either side for 3 or 4 millims. There are no 

 "brain-eyes"; in this respect P. singulare differs from all other known members of 

 the genus. 



Genital Organs. The outer chamber of the antrum masculinum is very large and 

 is provided with thick muscular walls, in which on the dorsal side the accessory 

 vesicles, the vesicula seminalis and part of their ducts are embedded. The accessory 

 vesicles are relatively small and their ducts short. In other respects the sexual 

 organs are exactly as in P. siphunculus. 



* In my list of the species of the genus Leptoplana given in the ' Proc. Zool. Soc.,' 1903, pp. 307, 308, 

 L. nationalis, v. Plehn, was by mistake referred to a division of section A of the genus which included 

 species in which the prostate gland is not chambered. It should, of course, be put in the division A (b) 

 near L. vilrni, Laxg. 



