CLASSIFICATION. 19 



the families in the main are compact and unquestionably natural assemblages, 

 in certain cases families as received by some are by others divided into two or 

 more, less comprehensive ones. I have here, in general, favored the narrower 

 limitation of the famihes; but it seems very convenient and desirable to have 

 names for designating a number of the obviously natural assemblages of such 

 families even though the majority of the families are left outside any such 

 grouping. I have accordingly introduced a number of superfamily names. 

 Thus, the elytra-bearing families Polylepididae, Sigahonidafe, Acoetidae, 

 Polynoidae, and Aphroditidae {i.e., the Aphroditidae sens. lat. of some 

 authors) are placed in a superfamily Aphroditoidea; the Leodicidae, Onuphi- 

 didae, Lumbrinereidae, and Dorvilleidae {nom. nov. pro Staurocephalidae or 

 Stauronereidae) in the Leodicoidea; the Glyceridae and Goniadidae in the 

 Glyceroidea; the Disomididae {nom. nov. pro Disomidae), Spionidae and Apis- 

 thobranchidae in the Spionoidea; the Spintheridae, Euphrosynidae, and Amphino- 

 midae in the Amphinomoidea; the Alciopidae, Lacydoniidae, lospilidae, Ponto- 

 doridae, and Phyllodocidae in the Phyllodocoidea; the Syllidae and Hesionidae 

 in the Sylloidea; the Serpulidae and Sabellidae in the Serpuloidae; and the 

 TerebelUdae, Ampharetidae, and Amphictenidae in the Terebelloidea. 



Key to the Families. 



a. Prostomium freely exposed. 



h. Body bearing true elytra Aphroditoidea. 



c. Elytra borne on all somites; neurocirri and dorsal branchiae rudimentary. . . .Polylepididae. 

 cc. Elytra not on all somites. 



d. Elytra alternating with cirri in the anterior region but in the posterior region occurring on 



all somites, these at the same time bearing cirri or cirrif orm branchiae Sigalionidae. 



dd. Elytra not thus arranged. 



e. Elytra and cirri alternating almost regularly somite by somite. Two pedunculate eyes 

 accompanied or not by sessile eyes; no facial tubercle; tentacles two or three; body 



elongate Acoetidae. 



ee. Elytra not thus regularly alternating with cirri, but occurring on somites II, IV, and V, — 

 or rarely on II, III, IV, and VI, — and on alternate succeeding somites to posterior 

 region and then on alternate groups of two or most posteriorly of three somites. 

 /. Pharynx armed with four horny jaws; two or three tentacles; no facial tubercle, or this 



but weakly indicated Polynoidae. 



ff. Jaws none or rudimentary; a median tentacle alone present; facial tubercle well de- 

 veloped Aphroditidae. 



bb. Body not bearing true elytra. 



c. Prostomium fused with the two succeeding somites and forming a head bifurcate in front and 

 bearing four tentacular cirri of which the posterior pair are much the longer; other somites 

 laterally prolonged and bearing biramous parapodia which are achaetous. . . . Tomopteridae. 

 cc. Not so. 



d. Anterior somites (excepting rarely the first one to four) with neuropodial processes or tori 

 nearly always more or less elongate at right angles to the axis of the body and linear, oval 

 or lamellar in form, which bear numerous crochets or uncini in unmixed groups or series, 

 or rarely the crochets few in number. 



