Polychacta. 267 



the erect setae of the dorsal fascicles and to the abundance and size 

 of the spines on the elytra. It is a variety to which the term spinosa 

 would be much more appropriate than to v. tijinca. 



I was at first tempted to place this species as a variety in the 

 series of H. spinosa, as I could find no essential divergence, except 

 in the character of the elytra, which are known to vary considerably. 

 But besides the fact that the collection contains no appreciable 

 gradation between this extreme variety and the typical form, there 

 is also a slight difference apparent in the setae (PL XLIII., fig. 3). It 

 will be interesting to learn, from the examination of a larger series, 

 whether or not the autonomy of this species can be maintained. 



With regard to the bidentation of the ventral setae, which is a 

 generic character of Hannothoe, in the present variety the sub-ter- 

 minal denticle is obsolete, but may be seen in very rare cases. 

 Prof. Mcintosh describes and figures it. Below the curved tip the 

 inner surface of the seta is convex, a point also noted by the author 

 of the ' Challenger ' Eeport. The ' Southern Cross ' specimens, however, 

 are a variety or sub- variety distinct from the ' Challenger '' specimens, 

 as shown by the chijracter of the elytral spines, which arc acuminate 

 at their tips in the former and laciniate in the latter (figs. 10-11, 

 PI. XLIII.). 



The two varieties are therefore as follows : — 



1. H. croseknsis, var. acuminata, n. 



2. II. crosetcnsis, var. laciiiiata, n} 



I counted thirty-eight segments (including the buccal), with 

 body-length of 23 mm., width 9 mm. over the setae, 6 mm. without 

 the setae. In the v. laciniata the slender elytral fimbriae are not 

 merely marginal or sub-marginal, but are scattered over the surface 

 in amongst the spines. 



Some of the individuals of H. spinosa are infested with crustacean 

 ectoparasites, which are attached to the body of the worm by a 

 rostral process which pierces the integument and appears to end in 

 a disc inside. These parasites superficially resemble the Saecopsis 

 terehellidis found on Terehellides strocmi rather than the Herpyllohius 

 arcticus which occurs on H. imbricata."^ 



Other specimens present peculiar growths upon the head, whose 

 nature I have not determined. 



^ The laciniate tips of the elytral spines of Laf/isca crosetensis are not noted by- 

 Prof. Mcintosh, op. cit. 



" Levinsen, G. M. R. : 'Om nogle parasitiske Krebsdyr, der snylte hos 

 Aunelider,' Vid. Medd. Copenliagen, 1877-8, p. 351. 



