266 MESSRS. HANCOCK AND HOWSE 



the bones themselves are present on a fragment of the slab that 

 was split off from the specimen. 



The enlarged portion of the anal fin (b) is pretty well dis- 

 played, immediately behind the ventral plates ; but the narrow 

 posterior part is scarcely traceable. 



The tail is well developed ; but half of the upper lobe is want- 

 ing. The under lobe shows distinctly the numerous short joints 

 of which the rays are composed, as well as their terminal bifur- 

 cations. This lobe is one inch and a half long. The scales (e) 

 and marginal plates, or fulcra (/), are well preserved on the 

 upper lobe. 



The last specimen (PL X., fig. 4) we have to describe is the 

 largest of the four ; it is five inches in length and two inches 

 and a quarter deep. The head is much crushed ; but the orbit 

 (u), the narrow elongated gill-plates (s), and jaws (p, q), are all 

 determinable, though much injured. The ventral plates are 

 confused and broken ; they occupy, however, their natural posi- 

 tion ; and a few of the compound columns are present, and can 

 be traced to the anterior lateral plates. The great abdominal 

 rods (o) are also conspicuous, inclining backwards, the lower 

 wide extremities in contact with the last ventral plate, and the 

 upper extremities leaning against and as it were, pushing back- 

 wards the lateral plates in the immediate vicinity of the abdo- 

 men. 



The lateral plates (g) and rods (i) are well preserved ; and the 

 series of lozenge-shaped areas (h) form a distinct line from end 

 to end, displaying better than any of the other examples the 

 elevated central ridges. The plates on the shoulder (f) are also 

 beautifully preserved in regular order, and exhibit, in great per- 

 fection, the ridges resembling mucus-tubes ; and the whole 

 series of the sigmoidal plates (j), with their rods (i), along the 

 ventral margin, can be determined ; and some of them are in 

 good condition. The hour-glass-shaped plates (k) are quite dis- 

 tinct, and are regularly arranged along the same margin ; and 

 those below the elevated portion of the dorsal fin are likewise in 

 excellent order. 



No distinct traces of either the pectoral or ventral fins are 



