47 108 Proceedings of the Royal Irish Academy. 



for this species. In 1870 Grube recorded C. norvegicus from St. Malo, 

 without giving any description. The description and figures given by Eathke 

 are very meagre ; and I have thought it desirable to give a full account of 

 this species. 



A single mature female was dredged in Clew Bay, in 5i-ll fms. Four 

 other specimens were available from various places on the Irish coast, and 

 have been utilized in drawing up the present description. 



The worms are 35-40 mm. in length, with 130-140 segments. The body 

 is rounded dorsally, flattened ventrally, with a shallow median groove. It is 

 widest and thickest between the 30th and 40th segments, and tapers 

 gradually towards both ends. The anus is large and funnel-shaped, with 

 crenulate margin, and with a rounded ventral papilla. 



There is a considerable amount of dark pigment on the ventral side of 

 the head and anterior region and in the lateral region of the prostomium 

 near the nuchal organs. 



The prostomium is followed by three achaetous segments. The first is 

 slightly elevated dorsally. The third post-oral segment bears a pair of cirri 

 (branchiae) on the postero4ateral margin (fig. 26 a). The position of the first 

 pair of lateral cirri has been utilized as a specific character by various 

 naturalists ; but I find them normally occurring on the third post-oral 

 segment in all species I have investigated. The dorsal tentacles (gills) are on 

 the fourth setigerous segment. There are nine or ten pairs of them forming 

 an oblique band on the sides of the segment, and leaving bare a broad median 

 area. Each segment, except a number at the posterior end, bears a pair of 

 lateral cirri, which are attached behind and above the dorsal setae. In the 

 anterior region the distance between the cirri and the dorsal setae is small, 

 considerably less than the distance between the dorsal and ventral setae. In 

 the anterior region also, the dorsal and ventral setae are further apart than 

 in the middle region of the body. Thus in the anterior region the space 

 between the dorsal and ventral setae gradually becomes less, whilst that 

 between the cirri and the dorsal setae increases. Behind the 20th segment 

 the ratio between these two spaces remains constant, the distance between 

 the cirri and the middle of the dorsal setae being two-thirds of that between 

 the middle of the dorsal and the ventral setae (fig. 26 b). This ratio supplies 

 a useful character for differentiating the species of Girratulus. 



In the anterior region of the body the feet contain only capillary setae. 

 The 10th segment has 13 setae in the dorsal division, 15 in the ventral, the 

 dorsal setae being somewhat longer than the ventral. There are three kinds 

 of setae. The longest setae are very slender, with flattened serrate blades. 

 The shorter setae are only half as long, but quite as wide as the long setae 



