A. M. Verrill — Marine Nemertecms of J^ew England. 447 



which are often bilobed ; anus at the posterior end of the caudal fin. 

 Lateral nerves large, not included in the muscular walls of the 

 body, united posteriorly. A median dorsal, and two lateral blood- 

 vessels are well developed. 



Muscular walls of the body are composed mainly of a thin, outer, 

 circular layer and a thicker inner, longitudinal muscular layer, in 

 which the fibers are arranged in distinct bundles, except in the thin- 

 ner marginal regions. A pair of long, muscular, cirriform appen- 

 dages is developed from the sides of the nuchal region in one genus. 



Nectonemertes, gen. nov. 



Body decidedly flattened and with thin borders along the sides ; 

 caudal fin usually broadest at the end and sometimes bilobed. Head 

 separated from the body by a more or less distinct neck-like portion. 

 Lateral cirriform appendages project from the neck or posterior part 

 of the head, in the adult. Mouth near the front of the head, just 

 below the terminal proboscis-pore. 



Proboscis long, slender, with a small bulb and sac ; its sheath ex- 

 tends nearly to the posterior end of body. Lateral lobes of the 

 intestine exist nearly to the end of the intestine, even into the cau- 

 dal fin. 



Special sense organs,* imbedded in the integument of the lower 

 side of the head, form a cluster on each side, their ends projecting 

 as small papilla?. Eyes of the ordinary type are, apparently, want- 

 ing. Probably the species are transparent in life and swim actively, 

 like Sagitta. 



Nectonemertes mirabilis Veiriil, sp. nov. 



I^LATE X.V.Wiri, FIGURE 1. 



Description of the adult: Size large, up to 2 inches or more in 

 length. Bodj' rather elongated, decidedly flattened and with 

 abruptly thinner marginal regions, smooth, with the walls somewhat 

 translucent, longitudinally and transversely striated, elastic ; in the 

 middle region of the body the sides are nearly parallel ; posteriorly 

 it narrows rather rapidly to the base of the tail, and at this place, in 

 some examples, the thin marginof the body forms a sort of fin or 

 thin rounded lobe on each side. 



*The precise nature of these organs has not been ascertained, but they are prob- 

 ably special sense organs. 



