38 THE ANNELIDA POLYCHAETA. 



cc. Non-pelagic forms; these pigmented and more or less opaque ; setae ordinary. 

 d. Elytra arranged in the usual manner in the family. 

 e. Somites more or less numerous, with the body long and vermiform; notopodia abortive, 

 with its setae few or none; elytra commonly much reduced in size. 



/. Ventral cirri bearing conspicuous wart-like tubercles Perolepis Ehlers. 



//. Ventral cirri as usual, smooth. 



g. Elytra occurring in pairs throughout Lepidasthenia Malmgren. 



gg. Certain somites having an elytron on one side paired with a cirrus on the other. 



Lepidametrea Webster. 

 ee. Body mostly short and depressed, proportionately broader, and somites fewer. 



/. First pair of elytra of normal size, all others exceedingly small; elytra twelve pairs; 



no notopodial setae Hermenia Grube. 



//. Elytra not thus. 



g. Median tentacle inserted dorsally. 



h. Inserted on the anterior region of the prostomium; notopodial setae coarser 



than the ventrals Alhnaniella Mcintosh. 



hh. Inserted on the posterior region of prostomium. 



i. Parapodia without notopodial setae Admetella Mcintosh. 



ii. Notopodial setae present, coarser than the ventrals Macellicephala Mcintosh. 



gg. Median tentacle inserted marginally. 



h. With a subtentacular process or " cirrus " ; dorsal setae coarser than the ventrals. 



Eulagisca Mcintosh. 

 hh. With no such subtentacular process. 



i. Notopodial setae finer than the neuropodials. 

 j. Prostomium anteriorly with distinct peaks which bear the lateral tentacles. 

 k. With vesicular expansions about bases of elytrophores and cirrophores; 



pairs of elytra twenty Phijsalidonotus Ehlers. 



kk. With no such vesicular expansions. 



I. Elytra eighteen pairs or more Halosydna Kinberg. 



II. Elytra twelve or thirteen pairs. 



m. Palpi short and blunt, exceeded by the tentacles; styles of lateral 



tentacles short and conical; eyes none Bathjnoe Ditlevsen.i 



mm. Palpi and styles normal, tentacles not exceeding the former; eyes 

 present. 



n. Elytra thirteen pairs Euphione Mcintosh. 



nn. Pairs of elytra twelve. 



0. Notopodial setae with series of pectinae Lepidonotus Leach. 



00. Notopodials of two kinds, one wholly smooth. .Thor mar a Baird. 

 jj. Prostomium without such anterior peaks; elytra fifteen pairs. 



Mahngrenia Mcintosh. 

 ii. Notopodial setae coarser than the ventrals. 

 j. Pairs of elytra eighteen, or more. 



I. Neuropodial setae with apices bidentate; pairs of elytra eighteen. 



Alentia Malmgren. 

 II. Neuropodial setae with apices entire; pairs of elytra twenty-one or twenty- 

 two Pseudohalosydna Fauvel. 



dd. Elytra arranged as usual anteriorly but occurring on all somites in the posterior region. 



Hololepida Moore. 

 bb. Lateral antennae inserted ventrally. 

 c. Body long and vermiform. 



d. Elytra completely covering the body; notopodial setae finer than the ventrals. 



Acholoe Claparede. 

 dd. Dorsum in part uncovered. 



e. Anterior elytra on somites 2, 3, 4, 6, 8, and 10 Hemilepidia Schmarda. 



ee. Anterior elytra as usual, on somites 2, 4, 5, 7, 9, and IL 



/. No notopodial setae; neuropodials with tips entire Heieropolynoe Bidenkap. 



//. Notopodial setae present. 



1 The number of pairs of elytra not d(;finitcly stated by Ditlcvsen for this genus, but presumably as 

 in Lepidonotus. Cf. Danish Ingolf-Expod., 1917, 4, pt. 4, p. 42. 



