LEODICID^ OF THE WEST INDIAN REGION. 113 



Genus ARABELLA Grube. 



A. E. Grube, Die Familien der Anneliden, etc., 1851, p. 45. 



Body elongated, slender, without prostomial appendages or gills, with rudimentary 

 dorsal and anal cirri. Two somites without setse, the first forming the posterior border 

 of the mouth. Maxilla with carrier prolonged into very long, slender processes, the 

 forceps plate toothed at the base. Three pairs of terminal toothed plates, of which 

 the proximal pair are much the largest. Sometimes the two proximal plates are unlike 

 in size, but this does not always occur. There is sometimes a fifth pair of plates, each 

 with one tooth. Mandible with shafts slender, pointed, and rather widely separated. 

 Usually with eyes on the prostomium. Only simple setse present in any part of the body. 



This generic name was proposed by Grube as either a distinct genus from Lum- 

 brinereis or a subgenus under it. By later writers (Schmarda, 1861, p. 115) a genus 

 Aracoda was founded, though the distinction between this and other genera is not clear 

 from Schmarda's description. He states that it may have 8 or 10 jaws (4 or 5 pairs), 

 de St. Joseph (1888, p. 229) groups as Aracoda those with 5 pairs of jaws and 1 achsetous 

 somite. Enters (1864-1868, p. 281) distinguishes Aracoda by the possession of 5 pairs 

 of jaws, but later (1887, pp. Ill and 112) he states that anterior teeth may separate 

 from a plate and thus appear to be a distinct plate ; hence the precise number of plates 

 is not a good criterion. Ehlers's Aracoda dentata (1887, p. 112, plate 34, figures 8, 9, and 

 plate 35, figures 1-4) is an Arabella and his Aracoda debilis (1887, p. 113, plate 35, figures 

 5-8) is a Drilonereis. Gravier (1900) makes the possession of 4 and 5 plates in the 

 maxilla and 2 and 1 achsetous somites, respectively, the distinction between Arabella 

 and Aracoda. Neither of these criteria seems to me a valid one, and I would merge 

 Aracoda with Arabella. Mclntosh (1910, p. 395) apparently reaches a similar conclusion. 



As I have stated earlier, it seems to me probable that there are always two achsetous 

 somites, though in some cases, owing to partial fusion, and in others, owing to imperfect 

 preservation, the distinction between the two is not clear. Arabella also may have either 

 4 or 5 pairs of plates in the maxilla. 



Arabella setosa, new species. 



(Plate 9, figures 10 and 11; text-figures 421 to 424.) 



A medium-sized species. The type was 130 mm. in length, with a prostomial width 

 of 0.5 mm. The greatest body width was 1.5 mm. 



The body shows no especially characteristic coloration beyond that due to the con- 

 tained blood and the surface iridescence, which are not noticeably different from other 

 members of this genus and from Lumbrinereis. Preserved specimens show dark trans- 

 verse bands, which are due to coagulated blood and have little or no diagnostic signifi- 

 cance. 



The prostomium (plate 9, figure 11) is conical and has two pairs of eyes; the outer 

 are the larger and are often less distinct, as if they were under a deeper layer of epi- 

 dermis; one of the two inner eyes is often double. The peristomium is usually wider 

 than the prostomium, but this condition varies with the degree of expansion. Later 

 somites behind the first increase in width to about the middle of the body. There are 

 two pairs of short conical anal cirri. 



The parapodia are all similar in form and are prominent from the very first. The 

 tenth (text-figure 421) has a short basal portion with a long posterior lobe. A tuft of 

 very stout setse extends from the setal portion. I could find no aciculse. 



The setse (text-figure 422) are similar throughout, each with a stout shaft bent and 

 somewhat flattened toward the end, the flattened portion being noticeably striated. 

 There is a narrow, colorless wing, the axial portion being yellowish brown. The setse 



