644 SIR c. ELIOT ON NUDiBRANons [Jvme 19, 



identical gorgeous coloration. But there are differences of detail 

 in the buccal parts, and the branchit^ of Chr. sykesi have not been 

 observed to be subdivided like those of Chr. ijwpinata or to be so 

 long. 



Casella. 



This genus, though offering hardly any structural differences 

 from Chromodoris, is easily recognisable by its undulated dorsal 

 margin, which is generally marked by a conspicuous border. 



Casella rubra Bergh, 1905, seems to be a distinct species, but 

 it may be doubted whether the other specific names cover more 

 than one species which appears in several colour varieties. 



Casella maccarthyi (Kelaart). 



Doris maccarthyi Kelaart. 



Chromocloris maccarthyi (Kelaart). 



Casella cincta Bergh. 

 ? Casella atromarginata (Cuv.). 



(Kelaart, 1. c. I. p. 292. Bergh in Semper's Reisen, xi. 

 pp. 462-3 ; xvi. 2, pp. 831-37 ; xvii. pp. 941-4.) 

 Two drawings are preserved and also a specimen from Ceylon. 

 The drawings represent a pinkish-grey Casella with the character- 

 istic strongly undulated margin. There are no spots or motthngs 

 of any kind, but the mantle is bordered Avitli bright blue, the 

 upper part of the rhinophores is blue, and there are indications of 

 blue on the stems of the branchise. The pi'eserved specimen 

 corresponds with the drawing. The colour is of a uniform greyish 

 yellow without a trace of spots. The mantle-edge is marked by 

 a purplish-brown border, with traces of an accompanying white 

 border particularly on the under side. The length is about 

 28 mm. and the maximum breadth nearly 20 mm. The mantle- 

 margin is strongly imdulated, but narrow, particularly behind. 

 The rhinophore-sheaths are distinctly raised, but the margins of 

 the branchial pocket are not elevated. The branchiae are retracted. 

 The buccal mass has been removed. 



There can be but little doubt that this is the Casella cincta of 

 Bergh. It has all the characters, except that the back is not 

 spotted and the foot is not bordered with blue. The branchire 

 are given as fewer (15 as against 22), but the difference is not 

 important, and it is very likely that the smaller branchiae were not 

 visible outside the pocket. The preserved specimen was not 

 opened in order to preserve the appearance. 



I think that Casella cincta and Casella atromarginata are merely 

 varieties of one species which shade into one another through 

 various shades of blue, purple, and black. If this is so, the species 

 must be called C. atromarginata (Cuv.) and the blue-bordered 

 form var. maccarthyi. If thought advisable, the term var. cincta 

 can be used for forms with a blue border and a spotted back. 



