ZOOLOGY. 



ORDER 5. The Elasmobranchii, including the 

 Sharks and Rays, correspond pretty closely with 

 the Cartilaginous Fishes of Cuvier. The skull is a 

 simple cartilaginous box, without sutures. The 

 vertebral column is more or less cartilaginous, 

 and the exo-skeleton is ' placoid ' in its character 

 that is, consists of bony grains or tubercles 

 scattered throughout the integument. The gills 

 are peculiar, in that the branchial laminae are 

 fixed like the leaves of a book to partitions which 

 divide the gill-chamber into a series of pouch-like 

 spaces, which communicate internally with the 

 pharynx, and externally by one or more apertures 

 placed on the side of the neck, there being no 

 operculum or branchiostegal rays. The structure 

 of the intestine and of the heart is the same as in 

 the Ganoidei. 



Sub-order (A). The Holocephali including the 

 Chimcera monstrosa, which often accompanies 

 herring shoals, hence called the ' King of the 

 Herrings.' It has the mouth terminal in position, 

 and only a single gill aperture on each side of the 

 neck, covered by an imperfect operculum. 



Sitb-order (B). The Plagiostomi, which have 

 the mouth transverse, and placed on the under 

 surface of the head. There are several apertures 

 representing gill-slits on each side of the neck. 

 It includes the Port Jackson Shark (Cestracion 

 Philippi) of the Australian seas, with its curious 

 pavement-like teeth, adapted for crushing the 

 Crustacea and mollusca upon which it feeds. The 

 Selachii, including the true Sharks and Dog- 

 fishes, also belong to this group. They are dis- 

 tinguished from other fishes by many peculiarities : 

 in several species, the young are produced alive, 

 the eggs being hatched within the body of the 

 parent ; and in others, the eggs are inclosed in 

 a horny casing, which has often long tendril-like 

 appendages, that coil around and attach the mass 

 to other bodies. This is the case with the eggs 

 of the common Dog-fish and Skate of our coast, 

 the receptacles being vulgarly known as ' sea- 

 purses.' 



The sharks are distinguished by their length- 

 ened spindle-shaped bodies, by the gill-slits being 

 placed laterally on each side of the neck, and by 

 the fact that the pectoral fins have the ordinary 

 form and position. The White Shark (Carchartas 

 vulgaris) is the most celebrated species of the 

 tribe, being, from its size and voracity, the terror 



White Shark (Carcharias vulgaris). 



of mariners in the seas it inhabits. It frequents 

 warm latitudes, but has occasionally visited the 

 British shores. It has been known to attain a 

 length of thirty feet, and the opening of the jaws 

 in the largest individuals is sufficient to admit 

 11 



with ease the body of a man. As the mouth is 

 placed in the under surface of the head, the fish 

 cannot bite while- in the act of swimming forwards, 

 so that a dexterous person has been known to 

 defend himself from its attack. The teeth are 

 triangular and lancet-shaped, with acute points 

 and edges, and form several rows ; they are not 

 fixed in the jaw itself, but in a muscular membrane, 

 by which they are erected and made to project 

 when in use, lying flat in the intervals. As the 

 foremost are torn away, they are replaced with 

 others, which are brought up from the rows 

 behind. The Blue Shark (C. glattcus], which 

 frequents the Mediterranean, is not unfrequently 

 a source of great trouble to the fishermen of our 

 coasts, on account of the injury which it does to 

 their nets. It sometimes attains the length of 

 eight feet. The Zygana malleus, or Hammer- 

 lieaded Shark, is a remarkable genus, so named 

 from the projection of the head at each side in 

 the form of a double-headed hammer, with an 

 eye in the middle of each extremity. The Fox- 

 shark (C. Vulpes) is a British species. It is also 

 called the Thrasher, from the use it makes of its 

 tail, the upper lobe of which is elongated and very 

 powerful. 



The last group, the Batides, including the Rays, 

 and Skates, and Thombacks (Raia clavata\ are 

 remarkable for extreme horizontal flattening of the 

 body, on the under surface of which, a little behind 

 the mouth, the gill-slits are disposed in two rows. 

 They abound rather in temperate than tropical 

 seas. The eyes are placed on the back or upper 

 surface. The most interesting of all is the Electric 

 Ray or Torpedo of the Mediterranean. It pos- 

 sesses an electrical apparatus, by which it can 

 ^ive a smart shock to any animal it touches. The 

 flesh of the ray is wholesome. The skin of some 

 of them is employed in the arts for polishing, and 

 from that of others shagreen is made. In the 

 Pristis, or Saw-fish, the body is not flattened like 

 the typical rays, but bears a resemblance in its 

 form and general characters to the sharks. Its 

 snout is extended like the blade of a sword, with 

 strong and cutting tooth-like spikes on both sides. 

 This fish sometimes measures from 12 to 15 feet, 

 and will attack and inflict dreadful wounds even 

 on large whales. Of the Scylliidce, or Dog-fishes, 

 three species are known on our coasts. They 

 are distinguished from the true sharks by their 

 oviparous reproduction. Their skin is used by 

 cabinetmakers as a fine rasp, under the name of 

 fish-skin.' 



ORDER 6. Dipnoi including only the singular 

 Mud-fishes (Lepidosiren) of the Gambia and the 

 Amazon. They are peculiar in that they exhibit 



Lepidosiren (Lepidosiren annectans). 



a distinct transition between the Fishes and the 

 Amphibia. They inhabit marshy places, and are 

 able in the dry season to bury themselves in the 

 mud, there remaining dormant until the return of 

 the rainy season. 



