LEODICID^ OF THE WEST INDIAN REGION. 71 



Marphysa nobilis Treadwell. 



(Plate 6, figures 9 to 12; text-figures 245 to 256.) 

 Marphysa nobilis Treadwell, 1917, p. 265, plate 3, figures 3-9. 



A large species, one of average size measuring 350 mm. in length, with a peristomial 

 width of 4 mm. and of over 200 somites. At somite 17 the width was 7 mm., but behind 

 this was a narrowing to the posterior end. These measurements were made on preserved 

 material. 



In life the body is flesh-color, due largely to contained blood, and is markedly 

 iridescent. The only pigmentation is on the tentacles, which are white with green 

 bands (plate 6, figures 9 and 10) and obscure yellowish spots on the anterior surface. 

 The color of the posterior parts of the body is largely due to contained blood as well as 

 to intestinal contents seen through the transparent body-walls. The red gills also 

 affect the coloration. 



The prostomium is plainly bilobed, though during life the depth of the median 

 depression may vary greatly. When fully expanded its anterior margin is nearly 

 straight, and the sides taper to a narrower base. The artist has drawn it as contracted 

 and has drawn the median tentacle lying over the central depression. The tentacles 

 are longer than the prostomium and are banded with green. Each green band lies in 

 a constriction, but this is not a true articulation. There is one pair of small eyes. 



The peristomium is about as long as the prostomium and is very faintly marked off 

 from the second somite (plate 6, figure 10). Later somites are very short, but become 

 much broader than the first (plate 6, figure 11). There are two pairs of anal cirri, one 

 pair much longer than the other (plate 6, figure 12). 



The gills begin as a single filament on somites 24 to 29 and become two-branched 

 a few somites posterior to this. Through the middle of the body they have from 6 to 

 8 branches and are long enough to meet across the mid-dorsal line (plate 6, figure 11). 

 Toward the posterior end they become smaller and eventually disappear entirely at about 

 45 somites from the posterior end. 



The first parapodium (text-figure 245) has rather prominent dorsal and ventral 

 lobes, with an unusually prominent cirrus-like, post-setal lobe. There are two short 

 black aciculse. In the tenth parapodium (text-figure 246) the setal portion is much more 

 prominent than in the first, its pre-setal margin being truncated, but its post-setal drawn 

 out into a broad triangular lobe. The dorsal and ventral cirri are nearly equal in size, 

 conical, the dorsal a little more pointed than the ventral and with a notch on its ventral 

 surface. Three very black aciculse protrude in front of the post-setal lobe. The one 

 hundred and fiftieth parapodium (text-figure 247) has a rounded post-setal lip, but this 

 is much shorter than in the anterior somites. The dorsal cirrus is shaped much like 

 that of the tenth, but is very small and apparently carried on the side of the stem of 

 the gill. The ventral cirrus is a mere knob on the end of a swelling. Two very black 

 aciculse are present. Toward the posterior end (text-figure 248) the parapodium 

 becomes more conical, but is in other respects much like anterior ones, the dorsal and 

 ventral cirri, especially the dorsal, becoming very slender. In addition to aciculse like 

 those farther forward, a ventrally placed and lighter-colored one appears. 



The simple setse (text-figure 249) are long and slender, their terminal portions 

 broadened, without fin or lateral denticulations. The compound setse (text-figure 250) 

 have their basal joints widened at the end and with rather strong denticulations, the 

 terminal joint long, sharp-pointed, and with smooth edges. Through the region of 

 the gills the compound setse have relatively much shorter terminal joints than farther 

 forward. There are two forms of pectinate setse. The first (text-figure 251) occur in 

 the anterior portion of the body. These have from 20 to 25 very small teeth, the ter- 



