740 OBSERVATIOXS ON SOME AUSTRALIAN POLYCH^TA, 



each cirrus, but the number varies with the length of the aj)pendage. 

 The segments of the body are, as as a general rule, about 2h times 

 as broad as long ; their lateral borders are strongly convex. Each 

 of them is crossed on the dorsal surface, about its middle, by a 

 narrow transverse impressed line, due to the presence in that 

 position of a narrow transverse band of muscle. The parapodia 

 are not prominent; they are bilobed, the lobes pointed; there is a 

 stout ventral cirrus which is a little larger than the parapodium 

 proper, with 15 to 25 compound setse. On the dorsal side of those 

 are three shorter acicula. 



The oesophagus is surrounded by a circlet of papillae and armed 

 with a single triangular, hyaline tooth. When retracted the 

 papillae are opposite the third segment ; the oesophagus, which is 

 short, extends from the fourth to the eighth segments; the gizzard, 

 which is also short, from the eighth to the eleventh. 



There are two short cajca. The epithelium of the intestine is 

 full of small, solid greenish granules. 



The hypoderm is fuil of oval unicellular glands, sometimes quite 

 clear, sometimes full of granules. All the specimens seen were 

 males. 



This species is not uncommon among mussels and ascidians on 

 the shores of Port Jackson. 



When compared with Grube's description of S. i(,mhricolor 

 one is struck by certain points of resemblance. Thus Grube 

 describes his specimen as marked on the dorsal surface with 

 grey transverse lines, and behind with impressed points, which 

 might perhaps be the expression in spirit specimens of the 

 markings described above ; but the apparent absence of acicula 

 and the smaller numbers of the setae in the S. umhricolor seem 

 to distinguish that species from the present one. 



The present species is also nearly related to two European 

 species — S. gracilis and aS'. hamata ; but differs from both of them 

 in the form of the sette and the greater shortness of the gizzard ; 

 from the former also, apparently in the greater length of the cirri. 

 It is likewise allied to S. simillima of Claparede. From S. 



