PACIFIC COAST OI,IGOCH.ETA. 147 



with two parallel grooves in the e(]uatorial region. The posterior somites are very 

 wide and four-ringed, but the segmentation is irregular. 



Ovipore a little interior to seta 1; nephropores outside of seta 4. 



INTERIOR CHARACTERS. 



Body-irall. There is a special zone of sense organs in the anterior somites as in 

 Benhamia, but they are more scattered than in this genus. The longitudinal muscles 

 run irregularl}^ with no trace of bipinnate arrangement. The strands are rather 

 .narrow. The longitudinal layer is very narrow, especially in the clitellum. The 

 transverse layer consists of only 3 to 4 strands. The hypodermis offers nothing of 

 special interest. 



The longitudinal layer in the clitellum is greatly diminished in thickness, most 

 so in the lateral and dorsal I'egion of the clitellum. Anteriorly in somites ii and iii, 

 the longitudinal strands leave the body-wall and spread out fan-shaped to the inner 

 wall of the prostomium, forming retractor muscles for the upper and lower lips. 



Arciform muscles. In somites xx, xxi and xxii we find on each side of the 

 ventral nerve-chord several oblique or aciforra muscles, running from the region of 

 the copulatory grooves to the region above the lateral setie, thus serving to depress 

 and relax the two grooves. These muscles are confined to a single row, and do not 

 show a complex arrangement, as is so frequently shown in oligochseta. 



Septa. The septa between somites vii and xiv are much thicker than the others, 

 especially thickened are those separating somites from vii to x. Those between x and 

 xiii are less thick than the anterior ones. The thickest septa, vii/viii, viii/ix, ix/x, are 

 much thicker than the body-wall. The most anterior thick septum is the one which 

 posteriorly bounds the gizzard (fig. 74). 



The septum next anterior to this, the one which separates the two gizzards, 

 presents the peculiarity of not being attached to the body-wall, between vi and 

 vii, but it extends forward parallel with the intestine and passes in front of the brain 

 on the upper side, while the ventral side is attached to the oesophagus below the 

 pharynx. It forms thus a sac, as in various species of Benhamia. Anterior to this 

 septum I find no trace of others. 



Alimentary canal. The pharynx is well developed and superposed by a very 

 large glandular mass, which consists of about six layers of lobes, attached to muscular 

 strands, as usual. The most posterior mass is the thickest. The discharge pockets of 

 these glands into the phar^-nx are much thicker than any I have seen in other species, 

 but are otherwise not of any characteristic construction. 



Septal glands are situated far back in somites vii to xi. They are of the same 

 nature as those which discharge in the pharynx, but I have good reasons to believe that 

 the glands in this species discharge in the tubular intestine. I have been able to 

 follow the discharge duct as far as to the muscular layers of the intestine, which would 

 hardly have been the case if the ducts had continued forwards into the j^harynx, as 

 do those of the forward septal glands in many genera. A peculiarity of these glands 

 is that they are especially developed on the ventral side of the intestine (fig. 75) and 



Memoirs, Vol. II, 5. January 6, 1896. 



