2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



species of archiannelids were represented while in those samples 

 from near the low water line only Protodrilus corderoi was found. 



This investigation is a contribution of the "Bredin-Archbold-Smith- 

 sonian Biological Survey of Dominica" and I wish to express my 

 thanks to Dr. Horton H. Hobbs, Jr., United States National Museum, 

 for making my participation in the program possible. I am also 

 indebted to Dr. Marian H. Pettibone and Dr. W. Duane Hope, USNM, 

 for their comments and suggestive criticisms of the manuscript. 



Genus Saccocirrus Bobretzky 



Saccocirrus archboldi, new species 



Figure 1 



The new species is based on 11 specimens, five mature females 

 and six immature specimens. The animals were studied alive but 

 six worms (two females and four immature specimens) were fixed 

 and later examined for futher details. 



Types. — One whole mount with three specimens is deposited in 

 the United States National Museum. Female holotype, and two 

 immature paratypes, USNM 34709. One whole mount with three 

 specimens is deposited in the American Museum of Natural History, 

 New York. Paratypes, one female and two immature specimens, 

 AMNH 3876. 



Type-locality. — Middle Bay, Dominica, British West Indies. 



The new species is dedicated to Mr. John D. Archbold, who has 

 helped support the present survey on Dominica. 



Description. — The living animals measure 4 to 6 mm in length 

 (the tentacles not included) and approximately 0.2 mm in width. 

 The animals have 60 to 84 segments. The color of the worms is 

 a light yellowish white and the greenish intestine can be seen through 

 the body surface. The two black eyes are comparatively large and 

 easily discernible in life. They are situated near the base of the 

 prostomial tentacles, the latter attaining a length of about QOO/j, in 

 the longest of the specimens. The tentacles taper gradually toward 

 their distal ends and are beset with sparsely scattered, rather stiff 

 sensory cilia, which are more numerous on the anterior side. The 

 posterior surface of the tentacles is corrugated even when held straight. 

 Stiff sensory cilia also occur on the anterior margin of the prostomium, 

 on the lateral sides of the body, and on the dorsal side of the anal 

 lobes. The nuchal organs are small, elliptic, ciliated pits and are 

 found immediately behind the tentacles (fig. la). 



The achaetous peristomial segment is twice as long as the following 

 setigerous segments. The mouth slit extends over the whole length 

 of the peristomial region and is fined by lips having a very active 



