448 A. E. Verrill — 3Iarine Nemerteans of Nevi England. 



The tail gradually thins out to the end and at the saine time in- 

 creases in width by the development of the thin marginal regions, 

 thus forming a true caudal fin, in form somewhat like that of a fish. 

 Its posterior mai'gin is emarginate in the largest specimens, with a 

 distinct notch in the- middle, Adhere the anus is situated, but in other 

 specimens it is truncate. The integument of the tail shows strong 

 longitudinal muscular fibers toward its base, while the edges are thin 

 and delicate. 



The head is ovate in form, narrowest, but obtuse, in front, consid- 

 erably flattened, and usually separated from the body by a distinctly 

 narrower neck. From the back part of the head, or commencement 

 of the neck, a long, tapering cirrus arises on each side. The cirri 

 have a thick, roundish, muscular base from which they taper gradu- 

 ally to the long, slender, lash-like, often coiled tip. These organs 

 seem to be mere extensions of the muscular walls of the body and 

 are not hollow. 



On the ventral surface of the head and occupying a large ovate 

 patch on each side, there is a group of small acute papillae, pro- 

 jecting slightly above the surface ; they are arranged in three or 

 four irregular rows, and are connected beneath the integument with 

 pyriform organs which can be seen by transmitted light as opaque 

 yellowish bodies. 



The proboscis-sheath is well developed and extends back nearl}^ to 

 the base of the tail, where it is abruptly naiTOwed to a short muscular 

 band that joins the wall of the body. The proboscis is long and 

 slender, with a small rounded muscular bulb* and a small saccular 

 organ, much as in ordinary Enopla, though relatively smaller. 

 When the proboscis is partially protruded, as is the case in one ex- 

 ample, it is somewhat clavatc distally and is covered with small 

 papillae. In transverse sections its structure is similar to that of the 

 typical Enopla; its internal glandular layer is thick. 



The intestine is large and straight ; its lateral pouches are large, 

 not much elongated, mostly bilobed distally, those in the tail becom- 

 ing small and simple. The generative organs, in the form of rather 

 large, round or ovate vesicles, occupy the lateral and ventral regions 

 of the body-cavity, between and beyond the intestinal pouches. 



In transverse sections the walls of the body are rather thin ; the 

 outer layer of circular muscular fibers is thinner than the inner 



*I have been unable to find any armature in the only specimen hitherto prepared 

 for this purpose, but the stylets, if they existed, may have been destroyed by the 

 acidity of the alcohol in which it was preserved. 



