POLYLEPIDIDAE. 91 



SiGALioN Cuvier. 



Regne Animal, ed. 2, 1829, 3, p. 207; Audouin & Milne Edwards, Ann. sci. nat., 1832, ser. 1, 27, p. 398; 

 Hist. nat. litt. France. Annelides, 1834, 2, p. 103, Kinberg ,(3fvers. K. vet. akad. Forh., 1865, no. 4, 

 p. 387; D,uiBoux, Bull. sci. France & Bclgique, 1900, 30, p. 115; McIntosh, British annelids, 1900, 

 pt. 2, p. 427. 



Thalanessa Baird, Journ. Linn. soc. London. ZooL, 1865, 8, p. 32. 



SiGALioN pouRTALESi Ehlers. 



Mem. M. C. Z., 1887, 15, p. 57. 



Locality. Gulf of Mexico: Sta. 2370 (lat. 29° 18' 15" N., long. 85° 32' W). 

 Depth 25 fathoms. Bottom of coarse grey sand and broken shell. 7 February, 

 1885. One specimen. 



POLYLEPIDIDAE. 



Of the five famihes of truly elytra-bearing polychaetes which are here made 

 to compose a superfamily Aphroditoidea, one (Polylepididae) is not represented 

 in the collection of the Albatross. This is a small family embracing but two 

 genera, each represented by a single imperfectly known species. They approach 

 the Sigalionidae in having composite setae but are distinguished particularly 

 in bearing elytra on all the somites. The prostomium bears a single tentacle 

 and a pair of palpi. The proboscis is armed with four horny jaws. The two 

 genera, as known from the original accounts, may be easily separated as follows. 



Key to Genera. 



a. With suctorial processes on dorsal and ventral surface of the parapoJia; setae all composite. 



Pdogcnia Schniarda. 

 aa. With no such suctorial feet; notopodial setae simple, the neuropodials composite. Pohjlepis Grube. 



Synonymy of Genera. 



The second genus was designated Lepidopleurus by Claparcde (Annelides 

 Chetop. Golfe Naples, 1868, p. 105) ; but as this name was previously used for 

 a mollusc, Polylepis, adopted by Grube (Annulata Semperiana, 1878, p. 16) 

 from Claparede's name for the family, may be used. Grube, however, from a 

 study of a specimen in Claparede's collection which he believes to be that author's 

 Lepidopleurus, doubts that this genus is in reality a member of this group as 

 he found an alternation of elytra and cirri in the specimen (see Jahresber. 



