1072 ON CHROMODOUIDS FROM THE RED SEA. 



bent rorls, not strictly bifid but sometimes bearing asmall tubercle 

 near the tip. The formula of the radula is 70 x 80.0.80 as a 

 maximum, but it is considerably narrower in the anterior part, 

 which is also mai-kedly darker in colour. There are thickenings 

 on the rhachis as in Ghr. reticulata but even more distinct. The 

 first laterals are of the usual flatfish shape and bear about 

 4 denticles on either side. The other laterals are rather tall, and 

 erect. They bear 8-12 very faint denticles, visible only under a 

 high power. The outermost laterals are irregularly shaped plates 

 with a few denticles at the top. 



In most respects this animal closely resembles Bergh's Chr. 

 inopinata. The remarkable coloration is almost identical (unless 

 the light area behind the rhinophores proves to be a characteristic 

 feature found in other specimens), but there are two differences. 

 In Bergh's specimen (1) the branching consisted of five tufts each 

 subdivided into 3, 5 or 8 plumes, (2) the teeth of the radula bore 

 5-7 distinct denticles. The first difference is hardly of specific 

 value by itself. Typically, the gills of Chromodoris are simply 

 pinnate but in some species they show a tendency to subdivide. 

 Still individuals belonging to such species have often normal 

 piiinate gills. The difference in the teeth is more imjiortant. If 

 the denticles as drawn by Bei'gh are not exaggerated, we must 

 either recognize two species (the present animal being charac- 

 terized by its teeth, simpler gills, and perhajDS some persistent 

 differences in coloration) or else admit that considerable variations 

 in the radula are possible. I am inclined to adopt the latter 

 alternative. It will be observed that though the appearance of 

 the teeth in the two specimens is different, this difference depends 

 not on an alteration of shape but in the greater or less develop- 

 ment of denticles. Thickenings on the rhachis seem to be 

 indifferently present or absent in several species. 



EXPLANATION OF PLATE LXI. . 



Fig. 1. Chromodoris reticulata from a living specimen. 



2. Chromodoris reticulata. Dorsal view of the mantle and part of body in the 



living animal ; enlarged. 



3. Chromodoris reticulata, (a) One of tlie lateral teeth from the middle of a 



half row; (b) thickening on the rhachis. 



4. Chromodoris tinctoria from a living specimen. 



5. Chromodoris tinctoria. Teeth : («) third lateral, (6) hitei'al from the middle 



of a half row, (c) outer lateral, (d) thickening on the rhachis. 



6. Chromodoris inopinata (?) from a living specimen. 



7. Chromodoris inojpinata, a lateral tooth. 



