78 coE 



is sometimes so much increased that it covers the whole ventral surface 

 in the region of the mouth, and gradually becomes darker toward the 

 tip of the snout, as well as posteriorly. The color of the ventral surface 

 is similar to that of the dorsal surface, but is commonly slightly paler, 

 especially anteriorly, and has a grayish tinge. 



No eyes were found. 



Size. — Length of largest specimens collected about 300 mm. ; width 

 in intestinal region 6 mm. 



The body is fragile, and the specimens are often broken in killing. 

 After preservation in formalin or alcohol the body tapers gradually 

 toward the narrow head, is widest in the posterior third or near the 

 posterior end, and greatly flattened throughout. The head retains its 

 long, pointed appearance, the tip is recurved, and the cephalic furrows 

 in most specimens are deep and widely open. 



Frontal sense organs. — On the exact tip of the head are three 

 rather deep and wide pits, easily overlooked in the entire animal, but 

 very conspicuous in sections. These are undoubtedly sensory in their 

 nature, and are lined with slender rod-like cells with especially large 

 cilia. Burger has described in detail such sense organs in Micrura 

 and Cerebratulus^ and somewhat similar ones in other genera. These 

 ' frontal organs,' as they are called, lie above the proboscis pore; one 

 of them is situated in the median line and the other two are placed 

 symmetrically on the antero-lateral margins. 



The brain is remarkably large, and the dorsal ganglia are much 

 larger than the ventral. The posterior ends of the long lateral furrows 

 are greatly expanded. 



Cerebral sense organs. — These also are very voluminous and are 

 continuous with the posterior ends of the dorsal ganglia. The canals 

 leading to the exterior are large, and open into the posterior ends of 

 the cephalic furrows. Internally each canal passes directly beneath 

 the dorsal ganglion to its internal ventral border, and then bends dorso- 

 laterally to the external border of the sense organ. These canals leave 

 the cephalic furrows far back of the cerebral commissure, and at about 

 the point where the ventral ganglia merge into the lateral cords. 



Nephridia, — The nephridial system presents remarkable deviations 

 from the type usually found in the genus. The nephridial canals ex- 

 tend throughout the whole length of the esophagal region, and com- 

 municate with the exterior by upwards of sixty efferent ducts on each 

 side. In the region of the mouth, or directly behind it, are one or two 

 nephridial tubules on each side, quite independent of the rest of the 

 system. Each of these tubules consists of a coil of fine canals lying 



