432 A. M Verrill — Marine Nemerteans of Neio Eagland, etc. 



Length of largest specimens observed, about 75'"'"; breadth, 1-5 to 

 2'"'" in extension. Described from life. 



Massachusetts Bay and Gulf of Maine, 45 to 110 fathoms, mud. 



Resembles the young of Cerebratulus luHdus T^, whicli occurs 

 with it. 



Cerebratulus Remer, 1804. 



. Meckelia Leuckart, Breves Anim., p. 17, 1828 (t. Rathke); Diesing, Syst. Helm. 



vol. i, p. 266, 1850. 

 Serpentaria Goodsir, Ann. Nat. Hist, vol. xvi, p. Si?, 1835. 

 Oerehratulus {jxirs) and Meckelia Stimpson, Prodrorans, p. 160, 1857. 

 Cerehratulm Mcintosh, British Annelids, Part T, Nemerteans, p. 194, 1873. 

 Cerebratulus (pars) Hiibreeht, Voy. Challenger, vol. xix, p. 37, 1887; Cams, Fauna 



Medit., p. 160. 



Body large, elongated, much flattened along the middle and pos- 

 terior portions and adapted for swimming by having the margins 

 produced and thin, mainly oAving to the unusual development of 

 the longitudinal muscular layers, which are greatly thickened, es- 

 pecially the outer layer, which, as seen in transverse sections, forms 

 a more or less triangular band, much thicker than elsewhere, (Plate 

 XXXIX, fig, 19, I). Transverse muscular l)undles running from the 

 upper to the lower sides of the inner surface of the body-wall (fig. 

 19, t') are also unusually well developed so as to aid in giving an un- 

 dulatory motion to the margin while swimming. 



Anterior or oesophageal region large, with rounded margins (fig. 

 20). Ca^cal appendages of intestine numerous and crowded, elon- 

 gated, more or less forked and lobed at the outer ends, the divisions 

 occurring partly horizontally, and showing well in sagittal sections. 



Head versatile in form, usually without ocelli. Cephalic lateral 

 slits or olfactory organs are large and deep. Mouth unusually 

 large, oblong or oval, rather far back. Proboscis very long and 

 slender ; in section showing decussated muscular layers medially, 

 above and below. 



Anal papilla or cirrus often long and slender, delicate, con- 

 tractile, often M'an ting owing to injury. Tt contains a continuation 

 of the muscular layers of the body-wall. 



Hubrecht has united Micrura to this genus, and in his report on 

 the Nemerteans of the Challenger Exp. he proposes also to unite 

 Lineus with it. 



Such a wholesale massing together of these groups seems to me 

 unnecessarj^ and undesirable, and is, apparently, only thought of be- 

 cause of the diificulty of distinguishing the generic position of alco- 



