THE SHADS, THE EELS, AND THE LAMPREYS 299 



naturalists as to the specific rank of the grig, or broad-nosed 

 eel — -an animal of precisely similar habits, so far as they are 

 known, and of very similar appearance to the common eel. 

 It has a broader head and blunter nose than the other ; but 

 -the feature which seemed to Dr. Giinther to justify its 

 recognition as a separate species is the dorsal fin, which 

 " begins further backwards, the distance between the com- 

 mencerrent of the dorsal and anal fins being shorter than the 

 head." It has a very wide range, being described in the 

 'British Museum Catalogue as inhabiting European waters 

 generally, the Nile, China, New Zealand, and the West 

 Indies. 



Third Sub-class: CYCLOSTOMATA : SUCKER-MOUTHED 



FISHES 



The British list of fresh-water fishes is brought to a close 

 by two species of the peculiar and archaic type Cyclostomata^ 

 creatures whereof the skeleton is entirely cartilaginous. The 

 vertebral column is represented only by the notochord, or 

 undivided dorsal chord ; there are no ribs, no, limbs, no 

 scales, and no real jaws, the mouth being suctorial, surrounded 

 by a circular or nearly circular lip. There is but one nostril ; 

 the reproductive organs are single, consisting of but one 

 ovary or milt in each fish ; and on each side are seven 

 branchial openings to the gills. 



First Family : PETROMYZONTID^E : THE LAMPREYS 



But for the presence of two rayed dorsal fins and a small 

 rounded caudal fin, the lampreys, both in appearance and 

 parasitical habits, are far more suggestive of large worms than 

 fishes. The skin is naked, and the body shaped like that of 

 an eel or worm. The mouth is suctorial, circular when open, 

 and forms, when closed, a longitudinal furrow ; not transverse, 



