SOME AQUATIC WORMS, ETC. 187 



utely forked near the free ends. The branching is 

 very uneven and is easily overlooked, one branch be- 

 ing very small, often scarcely more than a minute 

 linear projection. 



The ventral cilia are in two longitudinal lateral 

 bands, and the space between is clothed with short, 

 hispid, recurved hairs, two or more long fine bristles 

 projecting from the same part beyond the posterior 

 border, between the two caudal branches. 



3. Ch,«t(3notus lArus (Fig. 134). 



The whole upper surface is clothed with short, 

 conical spines in longitudinal rows, these appendages 

 being recurved and not branched. They are often 

 largest posteriorly. The mouth is not beaded. The 

 ventral cilia are in two broad longitudinal bands near 

 the lateral margins, and the intervening space often 

 bears two additional parallel lines of cilia, which may 

 be absent from some specimens. These cilia, as in 

 all the species, subserve locomotion. The egg is 

 smooth, or hispid with short hairs. 



4. Ch^T(5notus acanth6des (Fig.' 138). 



The upper surface of this form is. wondrously well 

 protected. It possesses both spines and scales, the 

 latter imbricated, and their somewhat pointed free 

 margins directed forward, each one bearing a small 

 supplementary scale or scale-like thickening on 

 its posterior part, from which springs a recurved, un- 

 equally furcate spine. Near the body-center the 

 dorsal surface is traversed by a series of large, stout 

 spines rising obliquely upward and backward, and 

 forming a kind of spinous hedge, the surface behind 



