A. E. Yerrill — Marine Nemerteans of New England, etc. 439 



arctic current, as off Gay Head, in 19 fathoms, and off Block Island, 

 in 29 fathoms. It is also found on the coasts of Greenland, northern 

 Europe, and Scotland. 



This species usually lives in burrows under stones, in muddy or 

 sandy places, at and below low-water mark, but when disturbed it 

 swims readily and rapidly with vigorous eel-like undulations of the 

 posterior flattened portion of its body, which is carried with the 

 greater diameter vertical while swimming. In this habit it agrees 

 with (J. lacteus and several other large species, but it is, perhaps, 

 more active and more vigorous than C. lacteus, and somewhat less 

 liable to disrupt its body when captured. Like C. lacteas it is oc- 

 casionally taken at night in surface nets, showing that it is nocturnal 

 in its habits and voluntarily leaves its burrows and swims free at 

 the surface. 



After long preservation in alcohol the slate-color of the body and 

 the white margins are often distinctly visible. In some alcoholic 

 specimens the small and slender anal papilla is still preserved, but it is 

 so fragile that it is generally lost during capture or in the violent 

 contractions caused by the alcohol. 



Our species is probably identical with the European species 

 named C. angulatus by Mcintosh, who supposed his species to be 

 the JPlanaria angulata of Fabricius (Fauna Grunlandica). The 

 latter is, however, our Aniph'qoorus angulatus, as stated on a former 

 page. 



Formerly* I supposed that the Greenland species named Planaria 

 fusca by Fabricius might be the brown variety of Lineus virldis, 

 but a more careful study of his description, in which the absence of 

 ocelli, the presence of lateral cephalic slits, the rounded form of the 

 anterior, and the distinctly flattened form of the posterior part of the 

 body are mentioned, has convinced me that the species he had in 

 hand was the common dark-colored, large, northern Cerehrattdus, 

 which has received many later names. His statement that it lives 

 in sand on the shores conflrms this view. Moreover, this same Cere- 

 brat'idus has been recently recoi'ded from the Gi*eenland coast and 

 referred to the Fabrician species by Levinsen, as quoted above. He, 

 however, adopts the later emended form of the name, quite unneces- 

 sarily it seems to me. Hence I have restored the original name, first 

 given by Fabricius to this species. 



* Proc. U. S. Nat. Mus., vol. ii, p. 185, 1879. 



