342 CEYLON PEARL OYSTER REPORT. 



I have no drawing of the form assumed by the animal when alive, but the shape 

 of the preserved specimen approaches so near to Casella that, taken with the manner 

 of arrangement of the branchiae, it raises a doubt as to whether the distinction 

 between the genera Chromodoris and Casella can be preserved or rather whether 

 the line of separation has not been drawn in the wrong place. 



Chromodoris tenuilinearis, n. sp. Plate III., figs. 11 to 15. 



There is a single specimen of the above, taken on the Cheval Paar. 



The length of the preserved specimen is 2 - 5 centims., its width OG centim. and 

 its height 0'8 centim. The mantle is smooth, long and narrow, slightly wider than 

 the foot and not reaching as far as it posteriorly. The foot has its margins adpressed 

 and extends behind the body for - 4 centim.; width of the body 0'5 centim. 



The ground colour is a dirty transparent white. The mantle is marked by inter- 

 secting diagonal broken lines of a pale greyish-green colour (Plate III., fig. 11). 

 The sides of the foot are marked with traces of similar lines. 



The branchiae are 8 in number, long, slender and limp, simply pinnate, issuing 

 from a collar about 1 millim. high. The rhinophores are long, slender and colourless. 



The radula consists of 66 rows, formula 71-0-71. One or two of the innermost 

 teeth on each side are trifid, the rest bifid. There is a trace of a median tooth on 

 the rachis. The outermost tooth is a flat plate with median notch, the 2nd tooth is 

 slightly hooked and distinctly bifid. 



The jaws are strong, divided into 3 parts, one median and two lateral. They are 

 made up of hooked plates regularly arranged in alternating rows. 



There was no further examination of the animal made. The markings are of a 

 rather unusual type in the genus Chromodoris, in which they usually consist of 

 brightly-coloured lines parallel to the sides of the mantle or longitudinally arranged, 

 or else of spots. 



The armature of the jaws and radula are paralleled in several species, notably in 

 C. semperi, Bgh. (9, p. 482, plate lii., figs. 1 and 2; plate liii., figs. 13 and 14), in 

 which they are almost identical. 



Casella cincta, Bgh. 



One specimen from Muttuvaratu Paar, length 2 - 3 centims., has its colour fairly 

 well preserved. It is of a dark claret or plum colour, fairly uniform, with a dark 

 green margin to the mantle and, less evidently, to the foot. 



The branchiae are about 28 in number, simply pinnate, reddish with a dark green 

 rachis. They are arranged apparently in two spirals, one on each side of the anus. 

 Anterior to the anus is one gill plume distinctly larger than the rest. 



The rhinophores are finely laminate, plum coloured, with a tinge of green at 

 the tips. 



The radula contains about 140 rows, formula about 63-1-63. The teeth are 



