coe: nemerteans of west and northwest coasts. 177 



ures 3 by 4 mm., from which the intestinal lobes extend laterally to 

 a depth of 15 mm. on each side. So great measurements as these 

 have never before been described for any species of nemertean. 



Habitat. — The single specimen described above was dredged by 

 the Albatross in the Gulf of California (Sta. 3001, 24° 55' N. Lat., 

 110° 39' W. Long.), at a depth of 33 fms. Bottom composed of fine 

 gray sand and broken shells; temperature 64° F. 



Micrura Ehrenberg. 

 Symbolae Physicae, Berlin, 1831. 



This genus includes mostly moderately small, slender forms, 

 generally less rounded posteriorly, and of rather more active 

 habits than Lineus. Its most marked distinction from the latter 

 genus is that the posterior extremity of the body is provided with 

 a slender, usually colorless, muscular caudal cirrus. This is formed 

 of a continuation of the muscular tissues and integument beyond 

 the posterior end of the alimentary canal. 



The proboscis is usually slender and comparatively weak ; the 

 proboscis sheath is sometimes considerably shorter than the 

 body. 



The species of Mickura are generally, though not always, more 

 brightly colored and have more distinct markings than do those 

 of LiNEus. The vast majority of the species are provided with 

 numerous ocelli, though some are blind. The head is slender, and 

 not distinctly separated from the rest of the body. The lateral 

 faces of the body are not provided with thin edges as in Cere- 

 BRATULus, the intestinal region is not so much flattened, neuro- 

 chord cells are present in comparatively few species, and none of 

 the species are able to swim as do all species of Cerebratulus. 

 The mouth is usually smaller than in Cerebratulus, and the 

 intestinal lobes are not so deep. 



Including four species which are described as new in the present 

 paper, there are eight species of this cosmopolitan genus which are 

 now known to occur in the regions included in this report. So far 

 as I can determine none of these forms have been reported from 

 other parts of the world. 



