202 THE ANNELIDA POLYCHAETA. 



All of the type-specimens as preserved are flexed into a semicircle, with the 

 concavity dorsal. The strongly narrowed anterior region, with the three pairs 

 of large elytra, give to this form a very characteristic appearance. Aside from 

 the pecuUar tentacle, the form of the notopodial setae of the most anterior 

 parapodia seems to be especially distinctive. 



Nereis Linne. 



Sj'st. nat. ed. 10, 1758, 1, p. 654; Cuvier, Rosne anim., 1817, 2, p. 524; Audouin & Milne Edwards, 

 Hist.nat. litt. France. Annelides, 1834, 2, p. 181; Ehlers, Borstenwiirmer, 1868, p. 450; St. Joseph, 

 Ann. sci.nat., 1897, ser. 5, 8, p. 285; McIntosh, British annelids, 1910, 2, pt. 2, p. 267 (in part). 



Lycoris Savigny, Descript. Egyiite. Hist, nat., 1809 [ = 1822], 1, pt. 3, p. 29. 



Nereilepas Blainville, Diet. sci. nat., 1828, 57, p. 469. 



Heteroncreis Oersted, Annulatorum Danicorum conspectus, 1843, p. 19. 



Mastigonereis Schmarda, Neue wirbellose thiere, 1861, 1, p. 107. 



?Johnstonia Quatrefages, Ann. sci. nat., 1849, ser. 3, 12, p. 304. 



Thoosa Kinberg, Ofvers. K. vet. akad. Forh., 1865, no. 4, p. 172. 



Hediste Malmgren, Annulata Polychaeta, 1867, p. 48. 



Praxithea Malmgren, Op. cit., 1867, p. 50. 



Nereis segrex, sp. nov.^ 

 Plate 32, fig. 3-5. 



General color yellowish, without markings. The tentacles and cirri are 

 whitish. 



The type is incomplete caudally. The portion present consists of thirty- 

 eight somites. It is 22 mm. long and has a maximum width, exclusive of para- 

 podia, of 3.2 mm., and inclusive of parapodia, of 4.6 mm., while to the tips of 

 the setae, the width is 6.3 mm. The body is widest anteriorly at about the sixth 

 somite, from where it narrows continuously caudad and also cephalad to the 

 second somite, which is narrower than the peristomium. The body is also 

 highest in the region of the greatest width. 



The prostomium in general outline as seen from above is roughly triangular. 

 It presents a short protrusion between the palpi which is truncate and bears 

 the tentacles. The dorsal surface in general is weakly and evenly convex except- 

 ing for a shallow and wide median depression anteriorly. There are no traces 

 of pigmented eyes, but colorless convex areas apparently represent them. Of 

 these the anterior ones are much the larger. The palpi are very thick and 

 extend forward nearly as far as the tentacles. Each is attached obliquely along 



' segrex, separated from tiie flock or company. 



