POTTS — POLTCIIiETA. 333 



species by their great size, equal length of all three tentacles, and large, rather flabby 

 elytra, with crest-like structures of varying development. In addition there is the 

 curious character noted by Gravier in the second segment, where the parapodium bears 

 ventral setae of a differomt type to those of tlie rest of the body, very fine, with a 

 membrane coiled round the shaft in a helicoid spiral. 



Gravier describes a thick lobe projecting from the surface of each elytron divided into 

 two by a median furrow. There is a spot of purplish-brown colour just in front of the 

 attachment of the elytron, and on the under surface a larger ring of the same colour 

 round the elytrophore. A number of small button-shaped jiapillse with tliree or four 

 projecting teeth were found on the surface of the elytron, but on the crest these were 

 replaced by a series of chitinous tubercles of greater size with a single acute tip. 



Generally the Zanzibar specimens agree with this account ; in particular they observe 

 the same peculiarities with regard to colour distribution. Only the elytral crests do 

 not possess the great conical papillae which Gravier and Mcintosh describe. Malaquin 

 remarks that the presence of these structures constitutes a difference from the type 

 specimen, and his examples from. Amboyna, as well as the present forms from Zanzibar, 

 agree with those which Grube originally described from the Philippines in the possession 

 of elytra with smooth crests. 



Localities. All from Zanzibar neighbourhood : — (1) Shore of Zanzibar. (2) Chuaka 

 Hd., low spring-tide. Mr. Crossland describes the elytra as " thick and sof lish. General 

 colour sandy grey. They are remarkably firmly attached. Dark brown mark over 

 elytrophore, larger dusky grey mark towards median line." (3) Mombasa. (4) Shimoni 

 shore. 



The two varieties which are next described clearly fall into tlieir place in this species. 

 The ornamentation of the elytron is indubitably related to and only sliglitly modified 

 from that in the parent type. There is no crest projecting from the surface of the 

 elytron, though in one case curious chitinous plates occur in the same position. 

 Mcintosh says, in speaking of L. cristatus and kindred forms: — "The parallel ridges 

 and tuberculated elevations on the scales of certain Australian Polynoida; in the British 

 Museum would seem to indicate stages in the production of these remarkable processes 

 {i. e. the crest)." The variations of tubercles on the elytra in this species are paralleled 

 for example in Eunoa nodosa, divided into various species by Hansen according to the 

 direction of variation *. 



Lepidonotus cristatus, var. ornata, var. n. (Plate 18. figs. 6, 7.) 



Measurements. Length 21 mm., width 10 mm. with setae, 6 mm. without. 



Median tentacle rather longer than the lateral. Two pairs of equal eyes, and definite 



nvichal collar with two lateral papillae as in L. c^nstatus. Elytra firmer than L. cristatus, 



with powdered appearance due to smaller tubercles. No crest but oval chitinous 



patches, generally three on each elytron, apparently formed from coalesced spines or 



* Hans Duncker, Zeitsclir. f. wiss. Zool. Isxxi. 1906, p. 236. 

 SECOND SERIES. — ZOOLOGY, VOL. XIII. 44 



