SABELLIDES AND SERPULIDES 205 



Genus Schizobranchia nov. 



Type, Schizobranchia insignis sp. nov. 



The three most typical species (insignis, nobilis, and concinna) 

 of this genus are remarkable for their large size and beautiful deep 

 wine-colored, much-divided branchiae. 



The small, nearly semicircular branchial lobes are simple, not 

 spiral, and bear long branchiae, stout at base, often irregularly arranged 

 in two series and usually regularly dichotomously divided from i to 

 6 times, so that the tips number several hundred. The ends of the 

 lobes are stiffened and protected by conspicuous, usually white, carti- 

 laginous edges. 



The two much smaller species (dubia and ajfinis), however, and 

 the young of these large forms, do not have all the branchiae forked, 

 but some are simple, thus showing a connecting link with species of 

 typical Pseudopotamilla, in which all the branchiae are simple. 



Eyes numerous, varying in size and arrangement along the back of 

 most of the rachises of the branchiae. 



Mouth protected on each side by three deep membranous frills or 

 folds. The two outer ones form a single membrane, which is attached 

 at one end to the inner surface of the ventral edge of the branchial 

 lobe, extends inward along the base of the lobe to about the middle, 

 then, folding on itself, terminates at the collar fastened to the side of 

 the ventral fissure. The inner one, next the mouth, is large, irregular, 

 somewhat leaf-like in form, deepest ventrally and abruptly tapered into 

 a long narrow end ; dorsally bearing a delicate filamentose tentacle, 

 which arises from the inner surface of the dorsal edge of the branchial 

 lobe. 



Collar four-lobed, as in Eudistylia and Pseudopotamilla ; deepest 

 along the sides beyond the small, angular, dorsal lobes, curving more 

 or less broadly and abruptly forward from the dorso-lateral notches, 

 ending in small angular processes on each side of the shallow ventral 

 fissure. 



Body long and usually slender, more or less compressed dorso-ven- 

 trally, very gradually tapered to the pointed posterior end. Dorsal 

 groove most conspicuous on the first segments. Fascicles of setae 

 similar in form to those of Eudistylia and Pseudopotamilla, usually 

 in a nearly straight series on the sides of the thorax, often oblique in 

 much contracted specimens. 



Setae similar in form to those of Pseudopotamilla. 



Chitinous tubes usually solitary when fully developed, twisted about 

 one another in colonies or groups when immature ; thick along their 



