108 



OF THE WEST INDIAN REGION. 



D. attenuata is difficult to collect because the animals live in small passages in the 

 hardest of the coral rock, and it is not easy to break the rock without injuring them. 

 Frequently on splitting the rock the animal will be seen stretched across from one piece 

 to another like a fine thread. The one figured was the first entire specimen obtained 

 in three seasons of collecting. The minute passages in the rocks so nearly fit the bodies 

 that it seems as if they must be made by the animals. Experiments indicated the pres- 

 ence of an acid secretion in the skin which may possibly have a function in this process. 



This species is common in the Dry Tortugas, Porto Rico, Montego Bay, Jamaica, 

 and Tobago. One specimen was dredged off Sand Key, in Key West Harbor. 



Drilonereis spatula Treadwell. 



(Text-figures 400 to 406.) 

 Aracoda spatula Treadwell, 1911, p. 6, figures 12-14. 



Collected at the Dry Tortugas and at Mangrove Key in Key West Harbor. At 

 the time it was not differentiated from a lot of Arabella and Lumbrinereis that were 

 collected with it, and since I was busy with other genera no drawings were made of the 



living animal and no notes of the coloration, 

 brown color, becoming slightly lighter toward 

 the posterior end. Some somites show a 

 median dark band. The prostomium (text- 

 figures 400 and 401) is very much flattened 

 dorso-ventrally, is about 2 mm. broad at the 

 base, and 2 mm. long. No eyes were visible, 

 but near the anterior border of the peri- 

 stomium there is a pair of shallow pits (sense- 

 organs?). 



The first two somites are short but wider 

 than the prostomium, and then the body 

 widens to about 4 mm. for the greater part 

 of its length. The parapodia begin on the 

 third somite and are at first very small, but 

 gradually increase in length on later somites. 

 They first assume a definite, easily distin- 

 guishable form on somite 23, but increase in 

 size posterior to this. Each (text-figure 402) 

 has a broad base of attachment, equal in 

 width to the length of the parapodium, and 

 carries a large ventro-posterior lobe. There 

 is a tuft of slender bilimbate setae and a 

 single large protruding acicula. 



Each half of the carrier of the maxilla 

 is oval (text-figure 403) and is continued 

 posteriorly as a long, slender rod. The for- 

 ceps is large and heavy, its terminal portions 

 much curved and with a very slender rod 

 running posteriorly from the base. This was 

 broken on the right side. Each of the next 

 pair of plates has 7 teeth, and on either side 

 beyond this are 2 plates, each with a single 

 tooth; the distal plate is slightly smaller than 

 the other. Ventrally is a black mandibular 



In alcohol the body is of a uniform dark- 



406 



TEXT-FIGURES 400 to 406. 

 Drilonereis spatula Treadwell. 



400. Lateral view of head x6. 



401. Dorsal view of head x6. 



402. Parapodium x34. 



403. Maxilla x!6. 



404. Ventral plate x!6. 



405. Seta xlOO. 



406. Acicula xlOO. 



