OPISTHOBRANCHIATE MOLLUSCA. 357 



compact, length 0'7 centim., without rachidian tubercles. The lamellae number about 

 2.t. The front of the toot Is divided into two lips by ;i transverse furrow, the lower 

 lip being the largest. The furrow does not extend laterally. The labial flap is 

 produced on either side into 2 very short tentacles split laterally at their extremities. 



The rhinophores are close together and rather short, tubular and split as usual. 

 The genital openings are close together at the commencement of the gill, but not 

 surrounded by a common investment. The penis is retracted. 



The shell, length 0"5 centim., lies well forward at about the anterior third of the body ; 

 the apex is pale, with embryonic spiral well marked ; the expanded portion is of a 

 horny yellow colour, strong, with well-marked longitudinal and transverse striae. 

 The teeth are of the usual type in Bcrthella, as defined by Vayssiere (9), knife- 

 shaped, with strongly denticiilated edges. They bear about 14 denticulations. 



The colour of the living animal as noted by Professor Herdman is " brilliant orange, 

 with white dots in little systems on the back." This differs somewhat from Ruppel's 

 description of P. citrin us as " pale lemon yellow, with large whitish irregular spots," 

 but as they agree otherwise there does not seem sufficient grounds for separating 

 them. P. angasi, Smith, from Port Jackson, agrees in many ways with this species, 

 but has only 16 gill lamellae. The figures of P. oblongus, Aud., given by Savigny, are 

 very like the Ceylon specimens and the figure of the shell of that species shows an 

 evident attempt to represent an embryonic spiral. 



Kelaart (2) has recorded this species as being of common occurrence in Ceylon ; 

 he gives the colour as orange spotted with white. 



Pleurobranchus hornelli, n. sp. Plate VI., figs. 1 to 5. 



There are in the collection some specimens of Pleurobranchus which I have not been 

 able to identify with any of the described species, and for which I accordingly 

 propose the above name. These are 7 specimens, 6 of which were taken by 

 Mr. Hornell from a buoy-rope at Galle in July, 1902, and one on Galle coral-reef 

 in August, 1902. Their colour, as far as is preserved, is a dirty white ground colour, 

 with the mantle covered with fairly close reticulations of brownish -purple. The 

 length of the largest specimen is 1"8 centims., width 1*2 centims., height 10 centim. 

 The mantle is about equal to the foot in front and behind, and a good deal wider 

 laterally. It is tuberculate, but the tubercles are indistinct, being crowded together 

 so as to produce a level surface (Plate VI., fig. 5), the margins of the tubercles being 

 only noticeable on account of the previously mentioned purple reticulation which 

 occupies the space between them. In the Galle coral-reef specimen, which seems in 

 a different state of preservation from the rest, the apex of each tubercle is raised into 

 a small papilla. 



The foot is moderately broad, with the front margin divided into two lips by a 

 transverse furrow. The upper lip is much thinner and somewhat shorter than the 

 lower. The furrow is continued laterally down one margin as far as the commence- 



