18 Annals of the South African Museum. 



ARENICOLA ASSIMILIS BHLEES ;;: VAE. AFFINIS 



ASHWORTH.t 



The specimens collected at Liideritzbucht (Angra Pequena) and 

 Table Bay belong to this species and variety, which has not hitherto 

 been recorded from South Africa. 



OCCURRENCE. 



Professor Gilchrist found these worms abundant, but only at one 

 place, at Liideritzbucht, between the town and Shark's Island. They 

 are not common in Table Bay and seem to occur chiefly in the area 

 uncovered only at very low tide. (Extract from Professor Gilchrist's 

 letter, dated October 11, 1910, sent with the specimens.) 



SIZE. 



About a score of specimens from Liideritzbucht and three from 

 Table Bay have been examined. Most of them range in length 

 from 60 to 85 mm., of which the tail forms 20 to 35 mm. ; three are 

 smaller and three are longer, the longest is 160 mm. (tail 85 mm.). 

 The larger worms are about 11 mm. in diameter at their widest 

 point, that is, about the fourth segment. 



COLOUR. 



All the specimens are now brown, for the most part light brown, 

 in colour. Professor Gilchrist tells me that those obtained in Table 

 Bay were of a striking yellow colour when alive. 



EXTERNAL FEATURES. 



The prostomium has the form typical of A. assimilis, that is, the 

 lateral lobes are in the form of a V, the limbs of which are of 

 uniform width, i.e., not dilated or lobate anteriorly, though they may 

 be curved (as in Text-Fig. V.). The extent of the protrusion of the 

 prostomium varies in different specimens ; in most cases the pros- 

 tomium is seen as represented in Text-Fig. IV., in a few it is 

 more fully extended or protruded, approaching the condition shown 

 in Text-Fig. V. The transverse diameter of the prostomium is 



* " Polychaeten " p. 104, in Hamburger Magalhaensische Sammelreise, Ham- 

 burg, 1897; see also Festschr. K. Ges. Wiss. Gottingen, p. 178, 1901. 



t Quart. Journ. Micr. Sci., vol. 46, pp. 737-785, 1903. The only differences 

 between A. asaiinilis and its var. a (finis are that the former has twenty chsetigerous 

 segments and the first gill on the eighth segment, while in the variety there are only 

 nineteen chsetigerous segments, and the first gill is on the seventh. 



