442 A. K. Verrill — 3farine Nemerteans of JVew England^ etc. 



In the classification adopted by Hubrecht and several other 

 writers this group and the Rhagadocephala (or ScJtizonertina) are 

 both raised to the same rank as the Eitopla. To rae they appear to 

 be of subordinate value, as here indicated. 



The species are all marine, and, so far as known, none of them 

 undergo a marked metamorphosis. 



Family, Cephalothricid^e Mcintosh, Nemerteans, p. 208. 



Uody slender. Head elongated. Superior ganglions and com- 

 missure situated decidedly in front of inferior ones. Cephalic fossa^ 

 and pits wanting. Ocelli usually few or absent ; sometimes numer- 

 ous. Two longitudinal blood vessels. 



Cephalothrix fErsted, Kroyer's Tidss., iv, p. 573, 1844. 



Astemma CErtsted, Kroyer's Tidss., iv, p. 574, 1844 (t. Mclntosli). 



Body slender, terete or nearly so. Head terete, much elongated, 

 tapering to a point in extension. Mouth small, situated far back. 



Cephalothrix linearis (Rathke) (Ersted. 



Plamiria linearis Jens Rathke, Skrivter nf Natiirhist. Selsk., vol. v, p. 84, tab. 3, 

 fig. 11, 1799. 



Planariafiliforrnis Johnston, Zool. Jour., vol. iv, p. 56, 1829 (t. Mcintosh). 



Nemerf.es {Borlasia) rufifrons Johnston, Mag. Zool. and Bot., vol. i, p. 538, pi. xviii, 

 figs. 4 and 5, 1837 (t. Mcintosh). 



Cephalothrix linearis G5rsted, Entw. Plattw., p. 82 (note under C. cceca), 1844 (t. 

 Mcintosh). 



Cephalothrix bioculato (Ersted, Kro3'er's Nat. Tidss., vol. iv, p. 573, 1844 (t. Mc- 

 intosh). 



Astemma fill formis iohn?,\.on, Catalogue Brit. Mus., p. 19, 18G5. 



Cephalothrix filiformis Mcintosh, Rept Brit. Assoc, 1867, Trans. Sect., p. 92, 1867. 



Cephalothrix linearis Mcintosh, British Annelids, Part I, Nemerteans, p. 208, pi. IV, 

 figs. 4 and 5; pi. xviii, fig. 15; pi. xxi, figs. 2, 8, 13; pi. xxni, figs. 12 to 16, 

 1873. 



Plate xxxvi, figures 4, 5; plate xxxix, figures 10 to 13, 14, 15. 



Body small, nearh' terete, changeable ; in extension very slender, 

 elongated, often linear or hair-like, fre(piently coiled in a close spiral 

 form, usually rather thickest in the middle and tapered both Avays, 

 but often with the posterior end thicker and obtuse. Head very 

 long and round, in full extension tapering to a slender sharp tip, in 

 contraction often circularly wrinkled ; usually, in mature specimens, 

 without distinct ocelli ; sometimes dark specks of pigment, irregu- 

 larly arranged, resemble imperfect ocelli. Young examples usually 



