184 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



smooth; somites XI-XVI are 3- or 4-ringed. The clitellar 

 somites are smooth, while those posterior to the clitellum 

 are distinctly 5-ringed. The prostomium divides somite I 

 by fully two-thirds. The clitellar somites are not very 

 prominent and evidently not fully developed. Sections 

 show that the clitellar glands are thin, extending dorsally 

 from XIIl-)^ XVIII, while ventrally they could be traced 

 to XXI. This posterior extension of the ventral part of the 

 clitellum is due to the high glandular ridge surrounding the 

 genital zone (fig. 146). 



Genital Zo7ie. — (figs. 145, 146.) This zone consists of 

 a deeply sunk rectangular field in XVIII-XX, surrounded 

 by a very high and swollen ridge of oval form, extending 

 across the largest part of the ventral surface in somites 

 XVII-XXI, where it connects with a low, median, ventral 

 ridge of the body-wall. There are generally no papillae, 

 but in one specimen there was a trace of a pair of papillae in 

 XVII. The prostate pores are strongly elevated. The 

 fossae connecting them are straight, and not curved as in 

 some other specimens. There are three pairs of small, 

 rather pellucid fields in XVIII, XIX and XX, which I take 

 to be tubercula pubertatis. Longitudinal sections show an 

 arrangement of glands in these places similar to those found 

 in tubercula pubertatis generally. 



SetcB. — The distances between the setae are not promi- 

 nently characteristic. Distance a— a is about three times 

 that of a-h. The ventral interval or a— a is only slightly 

 larger than the lateral interval or h-c. The latter, b-c, is 

 about four times as wide as a-b. The distance between 

 setae c-d is not quite twice that between a-b. The dorsal 

 interval or d-d is greater than half the periphery of the 

 equatorial. 



In somites VIII, IX and X the ventral interval, a-a, is 

 only about once and a half that of a-b, instead of being 

 three times as great as in the other somites. This is due to 

 the setoC ab being slightly more ventral in these three 

 somites. 



