472 FUNAFUTI ATOLL. 



A single specimen was taken in company with the Gorgonidw 

 described ante p. 308-320, by tangles hauled from eighty to 

 forty fathoms on the outer and western slope of Funafuti. It 

 differs considerably from a specimen (apparently typical) received 

 from New Caledonia, being of a chrome-orange colour, with a 

 pale peripheral band, 5 mm. long by 2 broad. Whereas the New 

 Caledonian example is of a peach-blossom pink colour, 6J mm. 

 long, 3 mm. broad, and of a stouter build. Both show the granu- 

 lations noted in the original description which Dall points out as 

 characteristic of the genus.* 



Garrett found this in Samoa and Fiji, and Melvill and Standen 

 received it in abundance from Lifu, Loyalties. f 



THETIDOS, gen. nov. 



A member of the Mangiliinse, distinguished by three stout 

 tubercles seated on the lip within the aperture, and by a globose, 

 tilted, two-whorled protoconch, which is closely spirally grooved 

 throughout. 



The new species, which typifies this proposed new genus, stands 

 apart from almost all Pleurotomida3, with regard to the few 

 large denticules which defend the aperture. The thickened lip and 

 anal notch throw it into Tryon's subfamily Mangiliinae, and among 

 the members of that, Glyphostoma makes the nearest approach. 

 Glyphostoma has smaller and more numerous denticules, and an 

 apex which in G. gabbii is thus described by Dall : " nucleus 

 acute, three-whorled, the first whorl smooth, rounded, tilted, 

 minute ; the others smooth, polished, keeled on the periphery."^ 

 This description fits others I have examined such as G. malleti. 

 In various instances the protoconch of Mangelia is shown by 

 Watson to have delicate, longitudinal ribbing. The genus Clathur- 

 ella has a peculiar raised mesh-work over all the whorls of the 

 protoconch, as here illustrated in the case of C. irretita, and which 

 has been beautifully figured in several instances by Watson in 

 the " Challenger " Report. The apex which Cossman gives as 

 characteristic of Clathurella is, however, quite different. 



Opinions on the systematic importance of the Pleurotomoid 

 protoconch are conflicting. Watson remarks that : " sculpture 

 and form of apex may probably serve as the safest basis of classi- 

 fication in the whole group."|| On the contrary Dall has expressed 

 his opinion that: "so far as our knowledge goes, nuclear 



* Dall Bull. Mus. Comp. Zool., xviii., 1889, p. 108. 



f Melvill & Standen Loc. cit., p. 402. 



j Dall Loc. cit., p. 109. 



Cossman Essais de Paleoconchologie comparee, ii., 1896, p. 122. 



|| Watson Chall. Eep. Zool., xv., 1886, p. 361. 



