LEODICID.E OF THE WEST INDIAN REGION. 



107 



Genus DRILONEREIS Claparede. 



E. Claparede, Les Annelides chetopodes, etc., 1870, p. 399. 



Body elongated, slender, without prostomial appendages, but sometimes with eyes. 

 Parapodia with a rudimentary dorsal cirrus and two sorts of simple setae, but without 

 compound or hooked forms. Anal cirri present. Maxillae resembling those of Arabella, 

 with long, slender, posterior processes on the carrier, the forceps much curved and some- 

 times denticulated at the base, the three pairs of terminal paired plates smaller and with 

 fewer teeth than in Arabella. Mandible frequently absent, very small if present. 



The genus was redefined by de St. Joseph (1888, p. 224), who thought that the 

 absence of the mandible, the difference in the form of the paired plates, and the much- 

 curved forceps separate it from Arabella. The species I have listed as D. attenuata 

 differs from the description in that the second pair of plates beyond the forceps are not 

 simple hooks, but have several teeth, a character which possibly should put this species 

 under Arabella. The prostomium is usually characteristic in that it is much flattened 

 dorso-ventrally. 



Drilonereis attenuata Tread well. 

 (Plate 9, figures 6 to 9; text-figures 395 to 399.) 

 Aracoda attenuata Treadwell, 1911, p. 5, figures 8-11. 



An extremely slender animal. The specimen figured was 175 mm. long, 0.33 mm. 

 wide, and had 875 somites. In life a faint yellow or flesh color shading toward light 

 green toward the extremities. In alcohol it is a light brown, but in many somites a 

 darker brown band encircles the somite at the level of the parapodia (plate 9, figures 6-9). 



The prostomium (plate 9, figure 7) is oval and capa- 

 ble of considerable changes of form. On either side near 

 the posterior end are eye-spots which may be covered 

 by the overlapping border of the peristomium. There 

 are no cirri. The pygidium has two equal paired lobes 

 (plate 9, figure 9). 



The parapodia begin on somite three (this was errone- 

 ously given as four in my earlier paper). They are all 

 alike in form, each having a bluntly ending setal lobe and 

 a longer postero-ventral one (text-figure 395). The figure 

 was drawn from the dorsal surface. Parapodia were absent 

 from a considerable extent of the posterior region and 

 here the somite boundaries are very difficult to distin- 

 guish. The simple setae (text-figure 396) have relatively 

 stout shafts, the terminal portion bent at an angle of 45 

 with the shaft and narrowing rapidly to an acute tip. 

 Along the angle are many fine denticulations. A very 

 few much smaller seta3 occur, whose tips just protrude 

 from the surface (text-figure 399). No distinct aciculte 

 were found, but if present it would be difficult to distin- 

 guish them from broken bases of ordinary setae. 



The maxilla (text-figure 397) is jet-black, with a very 

 long bifid carrier, the forceps fused at the base and much 

 curved. The first pair of plates have each 6 teeth, the 

 second pair 4, and the third 2. I was unable to find any 

 mandible, though there is a chitinous plate (text-figure 

 398) in the wall of the pharynx. 



399 



TEXT-FIGURES 395 to 399. 

 Drilonereis attenuata Treadwell. 

 x247. 



395. Parapodium 



396. Seta x394. 



397. Maxilla x!02. 



398. Ventral plate x!02. 



399. Secondary seta x310. 



