82 TRANSACTIONS LIVERPOOL BIOLOG-ICAL SOCIETY. 



striated, but so very finely, that the striae could be observed 

 by me with certainty, only at the head. The lateral 

 membrane (Seitenmembran), however, is very conspicuous 

 and broad, as it is 5 '8 /x broad in the middle of the body, 

 i.e., one-sixth of the body-diameter. 



As I have already remarked, this species is distinguished 

 from all others by the structure of the head. I did not 

 succeed, however, in elucidating that structure thoroughly 

 and completely. The head is not formed by six lips, as 

 was supposed by Cobb, who very likely has studied his 

 single specimen only in the lateral position, but by four, 

 namely, by two pairs of lips, which have a very different 

 structure. One lip is situated in the dorsal median line, 

 the other lip of the same pair stands, opposite the 

 former, in the ventral median line. The anterior or oral 

 surface of these two lips, which is non-transparent and 

 appears rather dark, is slightly convex, and terminates 

 externally with tioo sharp teeth, which are separated from 

 one another by a concave emargination ; these teeth, of 

 course, become at once visible in a front view of the 

 head. The posterior wall of these lips, by which they 

 are separated from the neck, is also thickened, and appears 

 consequently likewise dark, but the concave external wall 

 is not darkened (PL IV, fig. 2 a). On account of their 

 outer wall being concave, both lips appear in the usual 

 lateral position, as "conical lips turned outwards," as 

 writes Cobb, and in that position they are at once 

 conspicuous, even when only a little magnified, in con- 

 sequence of the dark colour of their anterior and posterior 

 walls. 



The shape and the structure of the two lips of the 

 other pair that stand laterally, did not become fully clear 

 to me, which ought to be ascribed to the fact that these 

 lips are not chitinous nor thickened, and consequently 



