VEBMES. 55 



already exists, or the covering is totally cast off when several new and 

 durable integuments may be generated, either speedily within short, or 

 leisurely at long intervals. 



In the following observations regarding form or appearance, I do 

 not aim at any thing more than recognition of the subject from external 

 aspect. 



I. GORDIUS. 



Body smooth, round, or flattened, sometimes very long, and casting 

 itself in a knot. Mouth a longitudinal slit in the under surface, some- 

 what behind the anterior extremity. Sides of the head cleft by a groove. 



This genus, which seems sufficiently definite as, 1. Gordius fragilis ; 

 2. Gordius spinifer ; and, 3. Gordius simplex.* 



The chief external characters of the genus, therefore, are a groove 

 on each side of the head, and a slit in the under surface for the mouth. 



1. GORDITJS FRAGILIS. Plate VI. figs. 1, 2 ; and VII. fig. 1. 



Having received the subject of this paragraph in the dusk as a fish 

 from its captor, I was induced at first to consider it as a kind of eel ; 

 nor would any ordinary spectator have probably thought otherwise. 

 In appearance, in colour, and in motion, it bore an intimate resemblance 

 to many specimens of the most common species. 



But this creature is one of the rarest, and among the most re- 

 markable animals of Scotland ; which, from certain external characters, 

 seems intimately allied to the Gordius race. 



It is infinitely the largest of any among the whole vermicular tribes 

 with which we are now engaged, that is, those void of obvious articula- 

 tions, and prominent external appendages. 



* Lamarck comprehends the genus Gordius under a section of the Planarian tribe. 

 But the definition proposed by him will not apply to those distinguished here by the generic 

 name. Tom. iii. p. 610. 



