DESCRIPTIONS OF GENERA AND SPECIES 301 



This species has been described by BOUSFIELD in two papers (2, 3), in the later 

 of which (3, PI. iv. fig. 8) the branchial area is illustrated. The definition does not 

 appear to me to be enough to distinguish it from D. perrieri, but, as BOUSFIELD 

 has examined both species, I leave it. 



(8) Dero multibranchiata, STIEBEN. 

 D. multibranchiata, STIEBEN, SB. Dorpat. Nat. Ges., 1892, p. 103. 



Definition. Length, 8mm. ; number of segments, 65. Branchiae fourteen in number, elongated. 

 JIab. Trinidad. 



This species, which has been somewhat fully described by STIEBEN (with a few 

 illustrations), is, of course, to be distinguished by the gills. The shorter dorsal setae 

 do not appear to be bifid. 



Genus CHAETOBRAWCHUS, BOUBNE. 



DEFINITION. Fore end of body with a series of pairs of hollow processes 

 of the body-wall, which enclose the dorsal setae, gradually diminishing in size 

 posteriorly. Dorsal setae, which commence in second segment,' capilliform, 

 increasing in length up to about the tenth segment; thence diminishing in 

 posterior segments; sickle-shaped setae also present; ventral setae entirely 

 uncinate. No glandular stomach. 



This is quite the most remarkable genus of the family at present known. Its 

 distinguishing feature is the presence of a double series of long hollow processes 

 of the integument, which enclose the dorsal setae, at least in the anterior seg- 

 ments ; posteriorly from the forty-second segment onwards, according to BOUBNE'S 

 figure (1, PI. xii. fig. i), some of the dorsal setae are not so enclosed. These 

 branchial processes, as BOUBNE assumes them to be, diminish in size after the first 

 dozen pairs until 'they become mere warts on the surface of the worm, and in the 

 posterior segments are entirely absent.' There are from sixty to seventy pairs of 

 them. Each process is hollow, its interior communicating with the coelom ; the 

 walls are formed of epidermis alone,- the muscular layers of the body-wall being 

 apparently not prolonged into it ; the epidermis has a cuticle, through, which project 

 very fine cilia ; at the extremity are a few stiff hairs, doubtless of sensory function, and 

 similar to hairs generally distributed over the body in the lower Annelids. Each 

 branchial process contains a vascular loop, which is derived from the circular vessel 



