468 THE ANNELIDA POLYCHAETA. 



forms have been found at depths of 600 and 700 fms, such as Sabella assimilis 

 Mcintosh and Sabella pavonina Savigny. While the great majority of sabelhds 

 are marine, at least four forms are at present known to occur in fresh or brackish 

 water. Manayunkia speciosa Leidy has been found in the Schuylkill River at 

 Philadelphia and in Egg Harbor River in New Jersey; and Caobangia billeti 

 Giard, living in perforations in the shell of a large viviparous Melania, is common 

 about Caobang, Tonkin (Giard, Compt. rend. Soc. biol., 1893, ser. 9, 5, p. 473). 

 And finally two species of Dybowscella, baicalensis Nusbaum and godlewski 

 Nusbaum, which hve in lake Baikal,^ the fauna of which in so many other branches 

 also strongly suggests its derivation from the sea. 



Since the tubes of sabelUds nearly always considerably exceed the dimen- 

 sions of the contained animals, the unoccupied space is taken advantage of by 

 various commensals and parasites. Such are various parasitic copepods; e.g., 

 Sabelliphilus elongatus Sars on Sabella sarsi Kr., Chonephilus dispar Sars on 

 Euchone papillosa Sars, Sabellachares gracilis Sars on Myxicola sarsi Kr., Gastro- 

 delphys clausii Graeffe on Distylia volutacornis Mont., and various others.^ 



Dybowscella shows a strongly marked sexual dimorphism. Certain sabel- 

 Uds are hermapkroditic, such as Amphiglena mediterranea Leydig. The sabellids 

 have a pronounced power of regenerating lost parts, particularly noticeable in 

 the case of the branchiae, which are frequently broken off. {Cf. Gravier, Nouv. 

 arch. Mus. hist, nat., 1908, ser. 4, 10, p. 298). 



Key to Genera. 



I. Thoracic somites with uncinigerous neuropqdial tori and notopodial capillary setae; alimentary 



tract well developed SaheUitiae, subfam. nov. 



a. Thoracic neiu'opodial tori bearing two kinds of setae ordinarily arranged in two rows. 

 b. Thoracic tori bearing avicular crochets and peunoned setae. 

 c. With a distinct collar. 



d. Basilar branchial lamina describing several turns of a spiral, 

 e. The two brancliial lobes unequal; setae of thoracic notopodia of one kind. 



Spirographis Viviani. 

 ee. The two branchial lobes equal; dorsal thoracic setae of two kinds. 



/. Branchial lobes spiral only in retraction; lower thoracic notopodial setae oblanceolate. 



Metalaonome Bush. 

 ff. Branchial lobes always forming a spiral. 



g. Collar with ends separated above; lower thoracic notopodials lanceolate. 



Distylia Quatrefages. 

 gg. Collar with ends meeting above; lower thoracic notopodials spatulate. 



Eudislylia Bush. 

 dd. Basilar branchial lamina not describing several turns of a spiral, 

 e. Dorsal setae of thorax of one kind. 

 /. Collar with two lobes; eyes on branchiae subterminal Branchiomma Kolliker. 



>Biol. centralbatt, 1901, 21, p. 6; also Gravier, Op. cil., p. 69. 



^ C/. St. Joseph, Ann. sci. nat., 1894, ser. 5, 17, p. 266, for original citations. 



