504 



PROCEEDINGS OF THE NATIONAL MUSEUM 



dividuals of a single species may have fewer or smaller paleae than 

 larger representatives. Aside from these gradations, there is remark- 

 able uniformity in structure of the different paleae for a particular 

 species. 



In other respects the species of Sahellaria are closely akin. The 

 body consists of an anterior prolongation or peduncle with a distal 

 operculum; the peduncle may have specific patterns of coloration. 

 The ventral mouth with its accessory parts (oral tentacles and paired 

 palpi) is located at the posterior end and ventral side of the peduncle; 

 it is usually not seen unless the several transverse rows of oral tentacles 

 are pushed aside. This is followed by the thorax, abdomen, and cauda. 

 The thorax consists of two anterior thoracic setigerous segments, rep- 

 resented by neuropodia only, and three biramous parathoracic seg- 

 ments, provided with alternating paleae and slender setae in notopodia 

 and limbate setae in neuropodia. The abdomen consists of a variable 

 number of biramous segments with uncinigerous tori above and slen- 

 der fascicles of setae below. This is followed by a slenderer, usually 

 cylindrical smooth cauda with a terminal anus. Branchiae are simple, 

 tapering, notopodial prolongations, usually somewhat crenulate at the 

 margins and present on most body segments. All setae are simple 

 but some are modified as paleae or uncini. 



Table 1. — Comparison of Western Hemisphere species and subspecies of Sabellaria 



•.See Hartman, 1944, p. 339. 



Table 1 lists the species and subspecies from the Western Hemis- 

 phere, with the distinguishing characteristics of the opercular paleae 



