166 THE ANNELIDA POLYCHAETA. 



bb. Tentacuhir cirri well developed; appendages swollen at base and pointed at tip; prosto- 

 mium and peristominm coalesced. 



c. Ventral cirri present, short and filiform Sphaerosijllis Claparede. 



cc. Ventral cirri absent MicrosyUis Claparede. 



aa. Witfi two pairs of tentacular cirri. 



b. Setae compound; tentacles and cirri fusiform, elongate Brania Quatrcfagcs. 



6b. Setae all simple Alluandella Gravier. 



II. Permanently P.\r.\sitic Forms. 



With a suctorial mouth and a retractile proboscis armed with two stylets operating like scissors; 

 prostomial appendages rudimentary; coeca of alimentary canal in each somite filling entire 

 body cavity. (Parasitic on the eel, Myrus vulgaris L., and probably other fishes). 



Ichthyotonms Eisig {I chthyotomidae) . 



Proboscis in the adult permanently e.xtruded, non-retractile, with no stylets, strongly chitinous, 

 deeply imbedded in tissue of host; prostomial ai)pendages not rudimentary; alimentary canal 

 without such coeca. (Parasitic on other polychaetes and on nemertines).. .Parasitosyllis Potts. 



Synonymy of Genera. 



Of the considerable additional number of generic names that have been 

 proposed in this family, most fall as synonyms in the system here accepted, 

 while others are too imperfectly known at present to be placed with certainty. 



Ancistrosyllis, established for A. groenlandica Mcintosh (Trans. Linn. soc. 

 London, 1877, ser. 2, 1, p. 502), is a hesionid. Langerhans's species albini 

 (Nova acta Acad. Caesareae Leop.-Carol., 1881, 42, p. 107), referred to this 

 genus, probably belongs in the Exogininae. In the latter the proboscis is 

 wholly unarmed and shows no subdivision into chitinous and muscular regions. 

 A dorsal aciculum is present in this species. 



Grube does not describe the proboscis of his genus Platysyllis, which accord- 

 ingly cannot be placed with certainty. From other characters Malaquin thinks 

 the genus in its relationship is intermediate between Trypanosyllis and Eury- 

 sylUs. 



Polynice Savigny and Amytis Savigny are doubtful genera, possibly near 

 or the same as Autolytus. 



HeterosyUis, estabUshed by Claparede for his species brachiata, a small 

 form only 2 mm. long and possessing twenty-three somites, is too imperfectly 

 described to be satisfactorily estimated. Other doubtful genera are Laomedora, 

 Lapithas, Periboea, and Thoe.^ Likewise doubtful is Umbellisyllis Sars. 



Cystonereis KolUker, Exotokas Ehlers, Oophylax Ehlers, Spermosyllis and 



1 Erected by Kinberg, Ofvers. K. vet. akad. Forh., 1865, no. 4, p. 249, 250. 



