420 THE ANNELIDA POLYCHAETA. 



secretion. Such a form is Terebella lapidaria Linne. Other species attach their 

 tubes to shells, rocks, corals, etc.; and Gravier {Op. cit., p. 211) mentions having 

 found numerous examples of Noimia medusa Savigny and one of Thelepus 

 thoracicus Grube in the canals of Hircinia echinata Keller. The mouths of the 

 tubes may be surrounded by long filamentous processes, or spines ( Dinar d, 

 Ann. sci. nat., 1894, 17, p. 185). 



Most known terebellids occur in the littoral zone, or at moderate depths, 

 though some descend to great depths, e.g., Terebellides eurystethus, sp nov. 

 (p. 438) which was secured off Peru from 2,600 fms. Eupistella (E^ipista) 

 darwini was dredged by the Challenger from 2,750 fms. 



Parasites are frequent upon or in the terebellids.^ St. Joseph notes the com- 

 mon occiu-rence of protozoan parasites such as Cothurnia, Rhabdostyla sertu- 

 larium Savigny, and Ophryodendron annulatorum. The crustacean TerebelUcola 

 reptans Sars was found originally attached to a large terebellid. Crypsidomus 

 terebellae was found by Levinsen in the intestine of Amphitrite cirrata. Distomes 

 often occur encysted in the anterior somites of terebellids. Southern mentions 

 the frequent occurrence of Polynoe scolopendrina in the tubes of Thelepus setosus 

 (Quatrefages), a species occurring on the Irish coast commonly under stones, 

 in Laminaria roots, and in Zostera beds. 



Key to the Subfamilies and Genera. 



a. Ventral plates developed. 

 b. Peristomium prolonged into a long papillose proboscis; uncini of thorax rostrate or crochet- 

 formed, those of abdomen avicular Arlacaminae. 



Filiform branchiae numerous, arising in fasciae on third, fourth, and fifth somites. 



Artacania Malmgren. 

 65. Peristomium not prolonged into a papillose proboscis. 



c. Prostomium short, with numerous tentacular filaments Terebellinae. 



d. Uncini pectiniform, not having transverse rows of denticles. Setae beginning on fourth 

 somite, occurring on seventeen somites, tips entire; uncini with 4-6 teeth, in a double 



series on part of somites; three pairs of arborescent branchiae Loimia Malmgren. 



dd. Uncini aviciilar, with transverse series of teeth at vertex. 

 e. With no branchiae. 

 /. Uncini with base long, the vertex relatively low, with 3-6 crenuli, 4-5 denticles in each 

 series. 

 g. Capillary setae beginning on fourth somite; setigerous somites few. 

 h. Setae all with tips similar. 

 i. Capillary setae with tips smooth; anterior and posterior nephridia subsimilar. 



Leaena Malmgren. 

 a. Setae with tips dentulate; anterior nephridia decidedly larger than the posterior. 



Lanassa Malmgren. 

 hh. Setae in part with tips entire and in part with tips dentulate .... Phisidia St. Joseph. 



' C/. Mcintosh, Ann. mag. nat. hist., 1894, ser. 4, 13, p. 9, etc.; Watson, Journ. Royal micr. soc, 

 1890, p. 685, pi. 14, f. 1-8. 



