166 THE ANNELIDA POLYCHAETA. 



?>6. Tentacular cirri well developed; appendages swollen at base and pointed at tip; prosto- 

 miuni and peristomium coalesced. 



c. Ventral cirri present, short and filiform S])haerosijllis Claparede. 



cc. Ventral cirri absent MicrosijUis Claparede. 



aa. With two pairs of tentacular cirri. 



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



bb. Setae all simple Alliumdella Gravier. 



II. Permanently Parasitic 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). 



I chihyotomus Eisig {I chthyoiomidae) . 



Proboscis in the adult permanently extruded, non-retractile, with no stylets, strongly chitinous, 

 deeply imbedded in tissue of host; prostomial appendages 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 gen-^ric 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 TrypanosylHs and Eury- 



sylhs. 



Polynice Savigny and Amytis Savigny are doubtful genera, possibly near 

 or the same as Autolytus. 



HeterosylUs, established by Claparede for his species hrachiata, 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 UmbeUisyllis Sars. 



Cystonereis KoUiker, Exotokas Ehlers, Oophylax Ehlers, Spermosylhs and 



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



