ACOETIDAE. 85 



deforming them and rendering a complete description impossible. However, 

 as the setae fm-nish clearly distinctive characteristics, it has seemed advisable to 

 describe and figure the species. Pontogenia sericoma Ehlers, also occurring in 

 the Gulf of Mexico, is at once to be distinguished from the present species by its 

 characteristically straight and strongly serrate dorsal setae; P. maggiae Augener, 

 taken in the Carribean off Montserrat, is also conspicuously different in the pre- 

 vaiUng form of its ventral setae as well as in the dorsal setae. 



ACOETIDAE. 



The members of this family have the body elongate, moderately flattened 

 dorsoventrally, and composed of numerous somites. 



The prostomium is without a facial tubercle. Eyes either all sessile or two 

 of them borne on conspicuous peduncles or ommatophores. Tentacles three, 

 two, one or none. Palpi present, long and subulate. 



Parapodia biramous. Elytra occurring on somites II, IV, V, VII and there- 

 after alternately with the notocirri. 



With setae either aU simple (Acoetinae) or in part composite (Peisidicinae). 



Proboscis at the end with a crown of numerous marginal papillae. Always 

 armed with four horny jaws. 



The acoetids are normally tubicolous. For special cases see, e.g., Watson, 

 Observations on the tube-forming habits of Panthalis oerstedi, Trans. Liverpool 

 biol. soc, 1895, p. 9; Ehlers, Mem. M. C. Z., 1887, 15, p. 56, under his ac- 

 count of Euarche tuhifex {Ewpanthalis kinhergi Mcintosh) . They are carnivor- 

 ous and the most voracious of the aphroditoids. 



Key to Genera. 



a. Composite setae present Peisidicinae. 



b. No dorsal cirri, somites not numerous Peisidice Johnson. 



bb. Dorsal cirri present; somites numerous Haswellia Darboux. 



aa. With no composite setae Acoetinae. 



b. Tentacles present. 

 c. With but two tentacles. 



Two ommatophores, branchiae present Eupolyodontes Buchanan. 



cc. With three tentacles. 



d. Two eyes borne on ommatophores. 



e. With branchiae; first pair of parapodia normal Acoetes Milne Edwards. 



ee. No branchiae; first parapodia modified Panthalis Kinberp;. 



dd. Eyes sessile, two or four in number Eupanthalis Mcintosh. 



bb. No tentacles; eyes sessile Resiio Moore. 



