11. ALEPIDOSAURUS. 421 



even the same species, in high latitudes of the northern and southern 

 hemispheres. 



Every part of the Alepidosauri is so fragile, that it is extremely 

 difficult to obtain perfect specimens. It is almost impossible to pre- 

 serve them in spirits without some portion of the dorsal and of the 

 other fins being broken. The entire structure of the dorsal fin is so 

 delicate, that it must even be liable to injury and alteration of outline 

 while the fish is in its native element. The fibrous ligaments con- 

 necting the vertebrae are very loose and extensible, so that the form 

 of the fish is easily lengthened when its body is slightly stretched. 

 Therefore no reliance whatever is to be placed on trivial specific dis- 

 tinctions founded on the form of the dorsal fin and on the relative 

 proportions of the head and body. A comparison of the two figures 

 of A. ferox given by Lowe will show the truth of this observation. 



The loose connexion of the single parts of the body is found in 

 numerous deep-sea fishes, and is merely the consequence of their 

 withdrawal from the pressure of the water to which they are ex- 

 posed in the depths inhabited by them. When within the limits of 

 their natural haunts, the osseous, muscular, and fibrous parts of 

 the body will have that solidity which is required for the rapid 

 and powerful movements of a predatory fish. That the fishes of this 

 genus belong to the most ferocious of the class is proved by their 

 dentition and the contents of their stomach ; but it is worthy of 

 notice that although the mouth is so deeply cleft, the lower jaw 

 cannot be moved from the upper at a greater angle than about 40°. 

 The teeth are constantly changing, and it is odd that an ichthyo- 

 logist like Lowe should have had so much difficulty in recognizing 

 the nature of some immature teeth lying in the gingiva. 



1. Alepidosaurus ferox. 



Alepisaurus ferox, Lowe, Trans. Zool. Soc. i. pi. 19, and p. 395. pi. 59 ; 

 Cuv. Sf Val. xxii. p. 529; Giinth. JVicf/m. Arch. 1860, p. 121; Peters, 

 Monatsber. Berl. Acad. 1861, p. 901 ; Johnson, Ann. 8c Maq. Nat. 

 Hist. 1862, x. p. 317. 



? Alepisaurus, Richards. Voy. Ereb. &/ Terr. Fish. p. 34. pi. 22. figs. 1-4. 



Alepisaurus azureus, Cuv. S\- Val. xxii. p. 530. 



B. 6-7. D. 41-44. A. 14-17. P. 14-15. V. 9-10. 



The length of the head is twice the height of the body, and rather 

 less than one-sixth of the total (without caudal). The eye occupies 

 the middle of the length of the head, of which it is one- sixth ; its 

 diameter equals the width of the interorbital space. Dorsal fin 

 much elevated. Pectoral elongate, but terminating at a great dis- 

 tance from the ventral ; the first ray of the dorsal, pectoral, and ven- 

 tral fins with the edge slightly serrated. Upper caudal lobe produced 

 into a long filament. 



Atlantic. Van Diemen's Land. 



a, b. Types of the species. Madeira. Fr©m the Collection of the 



Zoological Society. 

 c. Young. Taken from the stomach of specimen b. 



