1904.] PROM EAST AFRICA AND ZANZIBAR. 101 



My specimens seem to be on the whole smaller than those of 

 Bergh and to have fewer cerata. 



BoRNELLA DiGiTATA Adams. (Plate IV. fig. 5 a.) 



[A. & H., Notes on a OoU. of Nud. made in India, p. 140, 

 pi. xxxiii. figs. 8, 9 ; Bevgh, S. R. vii. p. 301 ; id. Danish Exp. 

 to Siam, Opisthobranchiata, p. 199.] 



Several specimens from Zanzibar Harbour (Bawi and Prison 

 Island). 



The living animals were white, with a granulated surface. On 

 the back was a reticulate pattern of deep orange. The cerata 

 were tipped with opaque white, below which was a band of bright 

 orange. The transparency of the body-walls varied in different 

 specimens. In some the liver and its ramifications were clearly 

 visible. 



The following description, when not otherwise stated, applies to 

 the largest alcoholic specimen ; the others are much like it, but 

 the smaller ones are only half the size. Length 30 millimetres, 

 breadth 4, height 8"5 ; much compressed laterally. On each side 

 of the mouth is a large bi-anched process with about fifteen sub- 

 divisions ; of these the four or five tippermost are larger and 

 digitate ; the remainder ai'e round and tubercular. The back 

 bears a pair of rhinophores with appendages, and, as a rule, four 

 pairs of cerata behind them. The largest specimens have a fifth 

 pair of small cerata, which in one case are fused together into a 

 single process. The rhinophore- sheaths are raised ; they bear in 

 front three small digitate pi'ocesses, and behind one long tapering 

 process which rises 5"5 mm. above the rhinophores. The first 

 pair of cei'ata are divided into two lai'ge and two small fingers ; 

 the right-hand member of the second pair into two approximately 

 equal fingers, and the left into two large and one small ; the third 

 into one large and one small finger ; the fourth are simple ; the 

 fifth are merely small warts. In the smaller specimens the first 

 pair of cerata are trifid only, and in the smallest bifid, with indica- 

 tions of an incipient third digit. It appears probable that the 

 number of digits increases with size and age. The first pair of 

 cerata bear three branchiae, the second, third and foui'th two, the 

 fifth none. The branchiae are all on the inner side of the cerata 

 and set close together. 



The labial armature consists of small overlapjping scales, arranged 

 in fairly regular rows. The edge of the jaws is quite smooth. 

 The radula consists of 34 rows. The median tooth has a long 

 central cusp, with from 8 to 10 denticulations or ridges at the base. 

 In most rows thei-e are 9 laterals, increasing in size from the 

 innermost outwards, but in some the niimber rises to 13 and 15. 

 The walls of the second stomach are raised into folds on which 

 are set large brown thorns, with rather blunt tips. The ramifica- 

 tion of the liver appears to be veiy irregular and to vary in 

 different specimens. In the largest the arrangement is as follows ; — 

 A single branch runs up into the tall tapering process behind each- 



