1903.] TROM EAST AFRICA AND ZAXZIBAR. 371 



this species, for these animals evidently undergo great changes, 

 both of shape and colour, in alcohol. 



13. Trippa monsoni, sp. n. (Plate XXXII. fig. 4.) 



One specimen dredged at Ohuaka on the East Coast of Zanzibar. 



I made the following description of the living animal : — About 

 one inch long and lively in its movements. The mantle ample, 

 covering both foot and head completely. The foot narrow, grooved 

 in front and slightly notched on the upper lip. The tentacles on 

 each side of the mouth white and conical. The whole body is of 

 a soft, spongy texture. The back is covered with small purplish- 

 white prominent reticulations and also bears white tubercles, 

 particularly on the edges of the mantle, branchial and r-hinophore 

 pockets. Both the tubercles and reticulations bear small papillas 

 or bristles. Between the reticulations are small purple pits and, 

 as a result, the general colour seems purple. Besides these, there 

 are four large pits, set symmetrically in a square in the centre of 

 the back. They are brownish at the sides and deep pui^ple at the 

 bottom. There are five other similar but rather smaller pits, 

 three in front of the rhinophores, one behind the gills, and one 

 placed quite symmetrically at the side of the upper right-hand 

 large pit. A white line runs round the edge of the mantle. The 

 rhinophores are yellow and finely perfoliate. The gills are usually 

 exposed, though they are completely retractile into a rather small 

 pocket. They are six in number, yellowish and tripinnate. The 

 under surface of the animal is purplish white ; there are no spots 

 on the foot, but two rows of purplish blotches on the underside 

 of the mantle. 



The alcoholic specimen is I'l centimetre long and "5 broad. It 

 is very spongy, like the living animal, but the colour has changed 

 to a uniform light yellow, Only the four central pits remain 

 distinct, the others having disappeared. There is no labial 

 armature. The radula consists of 28 rows of hamate teeth, 

 bearing three very small triangular denticles on the side of the 

 hook. The innermost teeth are small and less distinctly formed 

 than the others ; the three or four outermost are rudimentary, 

 and sometimes bifid or trifid. There is no genital armature. 



I think this form may be referi-ed to Trippa : the spongy 

 texture, the pits, and the small internal teeth all seem chai'acter- 

 istic. In making the dissection, I unfortunately omitted to search 

 foi- the ptyaline glands, and am now unable to say whether they 

 are present or not. 



14. Fracassa tuberculosa, sp. n. 



One specimen from the East Coast of Zanzibar on the reef. 



The living animal was of a dii-ty- white colour with dull green 

 patches on the centre and edges of the back ; the whole upper 

 surface was sprinkled with small bright blue dots with chocolate 

 borders ; also there were several dull yellow spots. The under 

 sxxrface was white with an irregular and indefinite network of dull 

 green. The junction of the foot with the under surface of the mantle 



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