264 Papers from the Department of Marine Biology. 



Marphysa viridis n. sp. 



The type specimen, preserved and much contracted, was 100 mm. long, 

 2.5 mm. broad at peristomium, and 5 mm. broad at point of greatest width, 

 which was at middle of body. It had approximately 200 somites. 



In life the head and first somite are of a decidedly greenish color; remainder 

 of body colored only by the blood seen through body-wall and gills. The 

 head is distinctly bilobed and capable of considerable changes of form (plate 2, 

 fig. 13). The tentacles are slender, colorless, and extend to the third somite. 

 In life the eyes are prominent, but become less so after preservation. In 

 preserved material the body as far as the ninth somite is very iridescent, but 

 behind this it is of a uniform grayish brown. 



Peristomium about as long as head, a little wider on posterior than on 

 anterior margin, and only faintly marked off from the second somite, which 

 is about half as long as it. Succeeding somites practically uniform in width 

 and length until they narrow at posterior end. Anal cirri inconspicuous, but 

 one of the two pairs much longer than the other. 



The gills begin in the type specimen on the right side on somite 25 with a 

 double filament; on the left they begin Avith one filament on 24, becoming 

 double on 25. In later somites the filaments increase rapidly in length and 

 new ones appear irregularly, the largest number I could find on the type 

 being 5. Toward the posterior end the number again diminishes, and the 

 last gill was on the twenty-fourth somite from the pygidium. The branches 

 of all gills are long and straight, but except in contracted individuals they do 

 not meet across the dorsal surface of the body (plate 2, fig. 14). 



First parapodium with dorsal and ventral cirri about equal in length and 

 with a conical post-setal lobe. The setal lobe bears several aciculse (plate 2, 

 fig. 15). The tenth parapodium with a rounded dorso-lateral post-setal lobe, 

 the setal portion with two lobes, one dorso-posterior, the other ventro-anterior. 

 The dorsal cirrus has a constricted base, then broadens, and finally narrows 

 to a rounded tip. The ventral cirrus has a broad base of attachment and is 

 bluntly rounded at apex. 



A parapodium from the middle of the body has rounded setal lobe, whose 

 anterior and posterior lips are about equal in size (plate 2, fig. 14). The 

 dorsal cirrus is small and does not extend much beyond the setal lobe. The 

 ventral cirrus has a broad base, and a small cylindrical terminal portion. The 

 gill filaments are about equal in length and arise from a broad base. There 

 are two dorsal aciculse having rounded ends, while a ventral acicula with 

 bifid end emerges just dorsal to the ventral cirrus. Behind the gill-bearing 

 somites the cirri become more prominent, the dorsal being the more slender 

 of the two. 



Simple setae slender with swollen pointed apex having entire edges. Com- 

 pound seta (plate 2, fig. 16) has prominent serrations on the end of the basal 

 joint, the terminal joint long, gently curved, without teeth. Pectinate setae 

 of two kinds ; in the anterior somites they have about 20 very minute teeth, 

 the end ones being a trifle longer than the others (plate 2, fig. 17). Posteriorly 

 are found asymmetrical pectinate setae (plate 2, fig. 18) flattened more than 

 the others and with only about 8 prominent teeth. In the middle somites 

 both kinds may occur. The dorsal aciculse are rounded at the end, and are 

 darker in anterior than in posterior somites. The ventral aciculse are lighter 

 in color than these, and are bifid at the end. In the posterior somites there 

 occur, what I could not find in the anterior, needle aciculae extending into the 

 dorsal cirrus. 



Jaws very dark, the forceps large with respect to the base, curved through 

 20. The proximal paired plates have 5 teeth on the left side and 6 on the 



