4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



ends with the seventh segment. The following part of the alimentary 

 tract shows (in living as well as in fixed specimens) intersegmental 

 constrictions. It continues to the beginning of the achaetous and 

 apodous posterior portion of the body, which comprises five to six 

 segments and the pygidium. In this body region the intestine is a 

 comparatively narrow and smooth tube that opens posteromedially 

 on the pygidium in a ciliated area (fig. 16). 



Each setigerous segment is provided with a pair of dorsolateral 

 parapodia that have a cylindrical shape and are about 80^ long. 

 Each parapodium is furnished with five setae of different lengths. 

 The longest seta (176ju) is flexible and hairlike and thickens slightly 

 toward its rounded distal end. The other four bristles (152ju, 123m, 

 98/x, and 74/x long) are broadened distally and bifurcated. The 

 symmetrical prongs have a blunt end with a shallow depression (fig. 

 lc). The pygidium shows two rounded lobes that are moderately 

 dorsoventrally flattened (fig. 16). Though the margins of the lobes 

 are somewhat wavy, there are no structures comparable with the 

 adhesive papillae in some other species of this genus. Over the entire 

 posterior aspect of the lobes, conspicuous gland cells are scattered 

 that, with their secretion, obviously function as an adhesive device. 



By examining the living mature worms, one finds the gonads in 

 the segments posterior from the twenty-fifth or twenty-sixth to the 

 beginning of the nonsetigerous body region. 



Diagnostic features. — Yellowish-white worms, 4 to 6 mm long, 

 with 60 to 84 segments; pygidium with two rounded anal lobes that 

 have no cirri or demarcated adhesive papillae; cylindrical parapodia 

 with five setae of which the longest one has a rounded tip and the 

 other four are bifurcated at their distal ends. 



Remarks. — To the genus Saccocirrus Bobretzky the following 

 species so far have been ascribed: S. papillocercus Bobretzky (1871), 

 S. major Pierantoni (1907), S. krusadensis Alikunhi (1943, 1948), 

 S. minor Aiyar and Alikunhi (1944), S. cirratus Aiyar and Alikunhi 

 (1944), S. gabriellae Marcus (1946), S. orientalis Alikunhi (1946), 

 S. pussicus Marcus (1948), S. parvus Gerlach (1953), and S. maculatus 

 Tenerelli (1964). One unidentified species of Saccocirrus was men- 

 tioned by Berkeley (1936). It corresponds in the character of the 

 setae to S. papillocercus, but the anal lobes are similar to those of 

 S. major. Marcus (1946), however, considered Berkeley's specimens 

 to be identical with S. gabriellae. 



According to body length and configuration of the pygidium, the 

 closest relatives of the new species are S. parvus Gerlach and S. 

 maculatus Tenerelli. Saccocirrus archboldi, however, is distinguished 

 from S. parvus by having longer and cylindrical parapodia with five 

 setae, while in S. parvus the parapodia are short, conical protuberances 



