PRINCIPAL DIAGNOSTIC CHARACTERS 



Pilargid genera are differentiated primarily by the presence and 

 shape of the emergent notopodial spines or hooks; the presence and 

 relative lengths of the head appendages; the development of the para- 

 podia; and to a lesser degree, the body shape. 



All genera, except Otopsis Ditlevsen, 1917, Pilargis Saint Joseph, 

 1899, and Lo andalia Monro, 1936, possess emergent notopodial spines. 

 They are strongly hooked in Sigambra F. Muller, 1858, and Ancistrosyllis 

 Mcintosh, 1879, and straight in Synelmis Chamberlin, 1919b, Litocorsa , 

 Cabira Webster, 1879, and Parandalia Emerson and Fauchald, 1971. Within 

 genera that possess emergent notopodial spines, their placement is of 

 specific importance, particularly in Sigambra and Ancistrosyllis. Vari- 

 ation, however, can be considerable and should be taken into account. 



Most genera possess at least two antennae and two pairs of tentacu- 

 lar cirri as well as a pair of palpostyles. Parandalia and Loandalia 

 lack antennae and tentacular cirri; Litocorsa stremma Pearson, 1970, 

 lacks antennae and palpostyles. The relative lengths of antennae and 

 palps, the number of antennae, and the presence of tentacular cirri 

 separate genera. All but the latter character are also important at the 

 species level. 



The parapodia may be sharply set off from the body, as in 

 Ancistrosyllis and Sigambra , or may be poorly differentiated, as in 

 Cabira. The shape and development of the dorsal and ventral cirri are 

 useful specific characters. 



Body shape, i.e., cylindrical or dorsoventrally flattened, is gen- 

 erally a consistent generic character. Some exceptions and uncertain- 

 ties do exist, however, so this character should be used cautiously. 



Pilargid neurosetae are simple, smooth to serrate, and grade in 

 length from long to short, terminating in fine, entire to bifid tips. 

 They are seldom useful as specific characters, although certain special- 

 ized neurosetae such as emergent spines and furcate setae may be impor- 

 tant. 



Some pilargids, particularly members of Ancistrosyllis and 

 Pilargis , have papillose integuments. The papillae are generally more 

 numerous on the dorsum, the head appendages and the cirri. The degree 

 of papulation may be of value as a specific character, although in some 

 cases it is considered quite variable intraspecif ically. Among the 

 material examined herein, it seems to be consistent and is considered as 

 such, although more material should be examined to support its use as a 

 diagnostic character. 



Pearson (1970) mentioned a curious dorsal organ in Litocorsa 

 stremma. It is located anteriorly within the body cavity, just beneath 

 the dorsal integument, extending anteriorly into the palps and posteri- 

 orly through about setiger 2 where it ends in two lobes, the tips of 

 which are pigmented. The entire organ is somewhat glandular and the 

 function is unknown. This organ has been observed by the author to 

 occur in other genera, and is well-developed in Litocorsa , Synelmis , and 

 Parandalia , where it extends posteriorly through 2-4 setigers. It is 

 less developed in most species of Sigambra and Ancistrosyllis , usually 

 not extending beyond the tentacular segment. Although the scope of this 

 chapter prohibits detailed systematic consideration of this organ, it is 

 figured when conspicuous. Certainly a detailed study of this organ 

 would be quite useful physiologically as well as systematically. 



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