358 THE ANNELIDA POLYCHAETA. 



kind only. The somites of the first division clearly longer than those of the 

 second. 



Branchiae beginning on somite VI. The first ones small, simple, and ligu- 

 late. In the posterior part of the anterior division some become two-branched. 

 In the anterior portion of the posterior division the branchia on each side of 

 each somite consisting of a transverse series of five or more long, cyUndrical fila- 

 ments arising contiguously and from a common low base. In the posterior 

 region the branchiae are again simple, one pair on each somite, and much 

 reduced. 



Genotype. — B. latum, sp. nov. 



This genus is nearest Scolopos from which it is most readily distinguished 

 by the highly and specially developed condition of the branchiae of the middle 

 region of the body and by the form of the peristomium, which in the second 

 genus is in the form of a truncate cone Avith no such great reduction on the 

 ventral side as occurs in Branchethus. 



Branchethus latum, sp. nov.' 

 Plate 64, fig. 7-11; Plate 65, fig. 1, 2. 



The body itself is brown throughout and with no special markings except- 

 ing on the sides of the peristomium, which are blackish or deep purplish. The 

 parapodia are paler, yellowish, and the setae are colorless, or very dilute, trans- 

 parent yellow. The branchiae are more or less tinged Avith purple, the seriate 

 ones of the middle somite appearing darkest, the most posterior ones light- 

 est. The tips of the neuropodia and its processes are in the middle region also 

 in part marked with purphsh. The notopodia are also marked with some 

 distal purplish areas. The postsetal processes of notopodia commonly have 

 a piirphsh spot on basal region, and those of neuropodia above at their bases. 



The body is very broad anteriorly, the greatest width being attained near 

 the thirteenth somite, from where the body narrows strongly cephalad, and, 

 beginning near the caudal end of anterior division of body, at first strongly 

 and then more gradually caudad, the posterior region becoming rather slender. 

 The dorsum is flat throughout. It shows a clearly impressed, median longi- 

 tudinal furrow. The venter is considerably flattened also in the anterior region, 

 where the depth of the body in proportion to the width is very small, while pos- 



' latus, broad. 



