In order to separate species of the Autolytinae, and certain other 

 genera such as Odontosyllis and Trypanosyllis , the pharynx must be 

 carefully dissected to determine its dentition. These dissections re- 

 quire good stereoscopic resolution due to the small body size of syl- 

 lids. One method of dissection involves making a' small dorsal incision 

 with a microscalpel, gently lifting the anterior end of the pharynx 

 through the incision with care not to sever the pharynx, and allowing 

 the freed end of the pharynx to rest on the dorsum. Muscle tissue 

 obscuring the distal teeth should be very carefully cut away. Clearing 

 of specimens may then be helpful by placing them in solution or on 

 temporary slide mounts using Amman's lactophenol (Cook and Brinkhurst, 

 1973) and heat (P. Wolf, pers. comm.), or Hoyer's (Coull, 1977). 



In the following descriptions of the Gulf of Mexico BLM-OCS species 

 of syllids, frequent reference is made to different body regions. Al- 

 though the body of a syllid is not externally divisible into distinct 

 regions, "anterior" here includes the body region from the prostomium to 

 the posterior end of the proventricle; "posterior" refers generally to a 

 few prepygidial setigers such as those of Syllis in which both superior 

 and inferior simple setae are present; and "midbody" refers to all other 

 intermediate setigers. 



Setal morphology and distribution are of paramount importance in 

 syllid systematics. Frequently it is necessary to describe the various 

 kinds of setae both along the body and within a setal fascicle, particu- 

 larly among the Syllinae and also to some extent the Eusyllinae and 

 Exogoninae. Setal morphology often changes considerably from anterior 

 to posterior along the body or from dorsal to ventral within a fascicle. 

 Blades of composite setae usually decrease in length from dorsal to 

 ventral. Blade-length ratios comparing the lengths of the longest and 

 shortest blades within a fascicle are reported for many members of the 

 Syllinae. Superior and inferior simple setae, which accompany the 

 composite setae in the posterior region of many species, are almost 

 always solitary, and are illustrated from the posterior body region 

 unless otherwise indicated. 



In many of the descriptions, morphological data are presented as 

 ranges for the following characters: number of articles in the antennae, 

 tentacular, dorsal and anal cirri; setal blade-length ratios; number of 

 setigers occupied by the pharynx and proventricle; number of marginal 

 pharyngeal teeth; number of muscle cell rows along the proventricle; 

 length ratio of the pharynx to proventricle; and the proventricle length 

 to width ratio. These ranges are based only on the material examined 

 for each species. The true population range for each of these parame- 

 ters may be somewhat broader. 



Setal blades were measured from the distal blade tip to the prox- 

 imal base that articulates in the shaft socket. Proventricle length and 

 width were measured at its longest and widest portions. 



BIOLOGICAL NOTES 



Syllids generally live in cryptic habitats, creeping actively 

 through the channels or crevices of sponges, corals, hydroids, algae, 

 gravel, etc. They are often the most abundant and diverse of polychaete 

 families in collections of living hosts such as sponges and hard corals. 

 Many syllids also commonly inhabit soft bottom sediments. 



30-3 



