BY WILLIAM A. HASWELL. 335 



Stylarioides Horstii, (Plate xxvi. figs. 6-8). 



Both of the specimens of this species that are at my disposal 

 are imperfect ; the more complete of the two is 1*5 cm. in length. 

 The longest seta? are 2*5 mm. in length. The greatest breadth is 

 3*5 mm. The number of segments is 39. 



The head and branchial apparatus are retracted in both speci- 

 mens, but, when dissected out, showed the following features : — 

 The tentacles are of about the length of the first six segments of the 

 body ; their greatest breadth is about one-seventh of their length. 

 They are deeply grooved longitudinally on the ventral side — the 

 ridges bordering the groove being convoluted — and are very finely 

 and closely corrugated transversely on the opposite side. The 

 branchiae, six (?) in number, are very long, cylindrical, and pig- 

 mented at the ends. 



The body is cylindrical, of nearly uniform breadth as far as the 

 33rd segment, though rather narrower at the anterior end ; 

 narrowing suddenly behind the 33rd segment. There is no 

 encrustation of sand-grains. The seta? of the first two segments, 

 about a dozen in number on either side in each, are greatly 

 prolonged ; they do not form a ring, but are arranged in definite 

 lateral bundles. They are exceedingly fine, and are divided by 

 transverse lines into numerous joints; they are covered with stalked 

 infusoria like the rest of the setae. The setso of the third segment, 

 4-5 in number, are more conspicuous than those of the rest of the 

 body, and are about half the length of the second segment ; there 

 appear to be no ventral setae on this segment. The remaining 

 segments all have dorsal and ventral setae, which are both longer 

 than is usual in this genus. Of the dorsal setas there are five to 

 eight in each bundle, many-jointed, very slender, tapering, — their 

 length nearly half the breadth of the body. The ventral setae, of 

 which there are 4-6 — usually 5 — in each fasciculus, are much 

 thicker than the dorsal, unjointed, laterally compressed, often 

 twisted, slightly hooked at the ends, much longer in the anterior 

 segments than they are further back. 



