1904.] FROM EAST AFRICA AND ZANZIBAR. 99 



in size. There are only very faint traces of a second row. The 

 radula consists of 37 rows, with a maximum formula of about 

 90+1.1.1 + 90. The teeth are of the shape usual in the genus. 

 The central tooth is finely striated, moderately wide and tricuspid, 

 the central cusp being pointed, those at the sides blunt. From 

 the buccal mass issues a long broad tube (4"5 mm. wide), which 

 passes above and to the left of the genital organs, and then enters 

 the liver, where it dilates into a stomach bearing a girdle of plates. 

 These are about 120 in number, horny, fairly strong, brown, 

 triangular, and of various sizes, the largest being 4 mm. long and 

 1"5 high, the smallest only a quarter of the size and white. The 

 liver is large, yellowish externally, blackish internally. 



In coloration this animal resembles M. cliloanihes B., but can 

 hardly be identified with that species on account of the difierences 

 in the velum, jaws, central tooth of the radula, and stomach-plates. 

 I think it is very probably identical with Pease's Tritonia hawai- 

 ensis from the Sandwich Islands, but his description is not suffi- 

 ciently detailed to make identification certain, and the expressions 

 " Veil strongly digitate," " Tentacles \i. e. rhinophores] retractile 

 into . . . laciniated sheaths," hardly apply to the present specimen. 



M. virescens and M. alho-tuherculata are closely allied and possibly 

 only varieties of one species ; but the present specimens exhibit 

 some differences in the velum, median tooth, and digestive organs, 

 as well as in coloration. 



Marionta, species. 



One small specimen, dredged in 10 fathoms off" Wasin. 



It was dead when found and of a uniform opaque white. The 

 velum was hardly digitate, but presented six undulations. The 

 foot was broad. 



The alcoholic specimen has become deep brown and is somewhat 

 decomposed. It is 5 millimetres long, 2 broad, and 1'5 high. 

 The back is tuberculate, with a slightly projecting margin, which 

 bears on each side 6 small branchiae set at a considei-able distance 

 from one another. The rhinophore-pockets are raised and simple. 

 The velum appears simply circular. 



No jaws could be discerned. The radula was extremely small, 

 and on a superficial examination appeared to be uniseriate, but 

 on careful investigation was found to have the formtda 5.1.5. 

 The laterals are all alike, thin and hamate. They are folded over 

 the central tooth, a narrow plate with slight indications of being 

 tricuspid. The stomach contained about 80 yellow plates, all of 

 much the same size. 



This is perhaps an immature form in which the jaws are mem^ 

 branous ; but, if so, it is remarkable that the stomaqh-plates are 

 fully developed. The extreme narrowness of the radula is also 

 remarkable. The chai'acters as described above are sufficient to 

 constitute a new genus, but I hesitate to do this on the evidence 

 of one minute specin:^en. 



7*- 



