BRANCHETHUS. 357 



few are shorter than the notopodial postsctal process ; but they increase in length 

 and breadth in going caudad and in the middle region exceed the postsetal 

 processes. In this region, however, a branchia laid transversely does not wholly 

 attain the base of the branchia of the opposite side. The branchiae continue 

 to the caudal end, but in the caudal region have become much reduced, more 

 conical in form, and smaller than the postsetal processes. The branchiae in all 

 cases are strictlv entire, none showing any such sUght tendency to bifurcate at 

 the tip as noted by Ehlers for Scoloplos cylindrifer. 



Locality. Paumotu Islands: Rangiroa Island, Mohican Reef. 23 Sep- 

 tember, 1899. One specimen. 



The form of body in this species is characteristic, widening from a little in 

 front of the middle both cephalad and caudad, somewhat as described for M. 

 longa Moore. From this form, however, it differs decidedly in various other 

 structural details, such as the proportionately longer prostomium, in having the 

 peristomium clearly shorter than the prostomium, in having the branchiae begin 

 on somite VI instead of on X to XII, the less filiform branchiae, etc. 



Branchethus, gen. nov.^ 



Prostomium in the form of a truncate cone with a more flexible process 

 or palpoid on the truncate surface, nearly as in Scoloplos, without eyes or ten- 

 tacles. 



Peristomium long above, but narrowing strongly ventrad and almost oblit- 

 erated in the midventral region. Proboscis short, and wholly smooth. 



Body elongate, much broader in anterior third than caudally; strongly 

 flattened above, convex ventrally. 



Body divided into two regions strictly distinct in the character of the 

 parapodia. In the anterior division the parapodia more lateral in position, with 

 neuropodia much elongated in the dorsoventral direction and bearing very nu- 

 merous, special, stout setae and longer, finer, capillary setae, both of which are 

 strongly annulated, the notopodium bearing setae of the finer type only. Pos- 

 terior border of neuropodium not festooned, but in the middle region bearing 

 a short, foUaceous, distinctly rounded postsetal flap. Parapodia of the second 

 and major division of the body with neuropodia not elongate dorso ventrally; 

 more slender and proportionately longer, and bearing setae of the long, fine 



' /?pa7x'a giUs, ^dos, character. 



