130 THE ANNELIDA POLYCHAETA. 



Most species of the family, as might be expected from their habits, are wide- 

 spread, only a few species, such as Vanadis antarctica, being restricted to one 

 ocean. 



The alciopids are represented but poorly in the collections made by most 

 exploring expeditions. Thus, in the extensive material secured by the Chal- 

 lenger, only five species occiu-red, two of these being present only as fragments. 

 This is due partly to the difficulty of collection and partly to the difficulty of 

 properly preserving these delicate organisms. The collections made by the 

 Albatross in the Tropical Pacific are interesting and comparatively rich, 

 particular attention apparently having been given to Plankton collecting by 

 the expedition of 1904-1905. Ten species are represented, some of them by an 

 abundance of material. Of these species, six are described as new, two of them 

 representing new genera. The number of species from the Pacific is thus 

 raised to seventeen. 



Key to Genera. 



a. Parapodia without cirriform appendages. 

 b. Setae all of one kind. 



c. Setae simple, capillary. Alciopa Audouin & Milne Edwards. 



cc. Setae composite Torea Quatrefages. 



6b. Setae of different types. 



c. Capillary setae and stouter crochets Corynocephalus Levinsen. 



cc. Composite setae and crochets Ploiohelmis, gen. nov. 



aa. Parapodia with one or two cirriform appendages. 



6. Each parapodium with a single cirriform appendage, 

 c. Setae all composite. 



d. First two somites distinct from each other Vanadis Claparede. 



dd. First two somites coalesced Mauita, gen. nov. 



cc. Setae of two different types. 



d. Simple capillary setae and crochets Callizonella Apstein. 



dd. Composite setae and crochets Rhynchonerella A. Costa. 



lb. Each parapodium with two cirriform appendages. 



Setae all composite Halodora Greeff . 



Alciopa Audouin and Milne Edwards. 



Cuvier's Regne anim. ed. 2, 1829, 3, p. 202; Ann. sci. nat., 18.33, ser. 1, 29, p. 236; Hi.st. nat. litt. 



France, Ann^lides, 1834, 2, p. 214; Apstein, Ergebn. Atlant. Ocean * * * Plankton-exped., 1900, 2, 



H. b., p. 6. 

 Alcinpe Ehlers, Borstenwtirmer, 1864, p. 176; Quatrefages, Hist. nat. annel^s, 1865, 2, p. 157. 

 Krohnia Quatrefages, Op. cit., p. 157. 



Alciopa cantrainii (Delle Chiaji). 



Greeff Nova acta Acad. Caesareae Leop.-Carol., 1876, 39, p. 57, pi. 1, f. 4, pi. 2, fig. 14-18; Ap.stein, 



Ergebn. Atlant. Ocean * * * Plankton-exped., 1900, 2, H. b., p. 7, pi. 5, fig. 53. 

 Naiades cantrainii Delle Chiaje, Descriz. anim. invert. Sicilia, 1828, 3, p. 155, pi. 155, fig. 14, 18, 21. 

 Alciopa reynavdii Kkohn, Archiv. naturges., 1845, 11, p. 172, pi. G, fig. 1-6. 



