416 THE ANNELIDA POLYCHAETA. 



incision on each side. Median ridge, or keel, long, extending to the caudal 

 marginal free border, and very high. Nuchal organs short, bowed mesad, an- 

 terior end not uncate. 



Anterior region irregularly pigmented. 



Each of the first four setigerous somites divided by an encircling transverse 

 furrow into two annuli, a narrow anterior one and a major posterior one which 

 bears the setae, and which has the anterior lateral border curved cephalad. 

 Between the anterior annulus of the first somite and the mouth a longer annulus 

 more or less clearly indicated by a fine furrow behind the mouth, and extending 

 to the incision between the lateral and caudal portions of the free cephaUc border 

 on each side. 



No uncini on first setigerous somite. Present on the second, third, and 

 fourth somites in a single series, and relatively few in number. On the fifth 

 somite they are abruptly much more numerous and are arranged in several 

 crowded rows (three in the genotype). On the immediately succeeding somites 

 the uncini mostly in two series, which may be irregular or incomplete. Uncini 

 with a long buried stem and a well-differentiated outer division, with teeth 

 moderately developed and several hairs below the major hook. Capillary setae 

 slenderly acuminate, limbate. 



Genotype. — S. meridionalis, sp. nov. 



This genus seems clearly to be most closely related to Maldane Grube and 

 Asychis Kinberg, of the subfamily Maldaninae. From both of these genera it 

 differs in having the uncini on some of the somites in two or more series. It is 

 much like Maldane in the character of the head-plate, e.g., in the long lateral 

 free borders, the high and long median keel, and the form of the nuchal organs. 

 It differs in apparently lacking the dorsal glandular area on the fifth setigerous 

 somite characteristic of Maldane. The genus is here placed in a distinct sub- 

 family, the Sonatsinae, as shown in the key (p. 409). 



SONATSA MERIDIONALIS, Sp. nOV.^ 



Plate 71, fig. 1-8. 



Greyish brown, the anterior portion with more darkly pigmented areas 

 that appear to have been bleached in preservation. 



Body widest cephalad, abruptly narrowing at the sixth segment, which is 

 broader anteriorly than caudally. On the sixth segment a broad glandular ven- 



1 meridionalis, southern. 



