406 ON NUBIBEANCHS FROM EAST AFRICA AND ZANZIBAR. [Mar. 1, 



lai-ge posterior tubercle. The openings of the rhinophores have 

 slightly raised but smooth edges ; the rhinophores themselves are 

 long, straight, and thin, and bear about 30 perfoliations. The 

 tripinnate branchiae appear to be nine in number, but are so 

 deeply cleft that it is hard to say how large a group should be 

 taken as the unit. The foot is narrow and not very clearly marked 

 ofF from the head ; it is distinctly but not deeply grooved in front. 

 The internal anatomy is as described by Bergh. Both the labial 

 armature and the radula are bright yellow. The former consists 

 of small rods, straight or bent, but in all cases hooked at the end 

 and not bifid. The teeth of the radula are somewhat irregular in 

 shape, but no denticulations are discernible : the innermost teeth 

 close over the rhachis. The oesophagus widens out into a distinct 

 dilatation before entering the liver. 



EXPLANATION OF THE PLATES. 



PlATE XXIII. 



Fig. 1. Chromodoris reticulata (p. 386). Anterior end, showing relations and 

 proportions of head, foot, and mantle, a, ridge connecting head and foot ; 

 b, groove in anterior edge of foot ; m, mouth. 



2. Diagram of the arrangement of the gills, the positions of which are shown by 



transverse sections of their bases : a, anus. 



3. A single gill cut across, showing ?'., rachis ; h.v., blood-vessels ; and j>., portions 



of three of the pinnse borne on the sides of the rhachis. 



4. Portions of the radula. a, central teeth ; b, the form of the majoritj'' of the 



teeth ; and c, those intermediate in shape and position between a and b. 



5. The alimentary canal. The liver is cut away and the stomach laid open. 



b. Buccal mass. 

 ff. Gills. 



I. Cut surface of liver. 

 Id. Ducts of liver opening into 

 stomach. 



sal. Salivary gland of right side. 



st.c. Thin-walled anterior diverticulum of 



stomach. 

 st.m. Muscles in stomach-wall. 



6. C. sykesi (p. 387). A living example. 



7. G. cava, from life (p. 388). m, edge of mantle ; f, edge of foot. 



8. Diagrams of the arrangement of the gills, a, from an example which had 



16 gills ; b, from one with only 12. 



Plate XXIV. 



Fig. 1, Chromodoris annulata (p. 389). Central teeth of radula. 



2. Diagram showing positions of bases of gills : a, anal papilla. 



3. A living example. The purple border of the mantle is continuous all round, 



but is in this case hidden in places by the folding down of the ft'ee mantle- 

 edge. 



4. C. elizabethina, var. africana (p. 392). 



5. C nigrostriata (p. 394), dorsal view. 



6. Side view of the same. (The number of branchiae was in reality seven, not 



nine as here depicted.) 



7. C. lineata (p. 396). Teeth of radula : a, from outer, and b, from central part. 



8. C.flava (p. 399). Living specimen, a. Anterior corners of foot, which may 



or may not project beyond mantle-edge {cf. lig. 9). 



9. Ventral view of the same showing narrow foot with its prolonged anterior 



corners and transverse groove, and proportions of head and mantle. 



