90 Part second. 



The Smooth-hound or Ray-toothed Shark, Mustelus (Fig. 60), is 

 only rarely to be seen in the Aquarium. This is one of the most 

 harmless of sharks; its blunt flat-topped teeth are not fitted for devour- 

 ing anything but crabs and mollusks, which it captures at great depths. 

 When placed in tank Nr. 10, it swims about at first in a very lively 

 manner with most graceful movements of its glossy body, but it soon 

 tires, and finally cannot lift itself from the bottom of the tank ; nor will 

 it touch any food in captivity. Its flesh is quite good eating. 



The Angel-fish or Squatina (Fig. 63), which forms a connecting link 

 between the Sharks and the Rays, is an unsightly beast, always lying on 

 the bottom of tank Nr. 10, and usually looked upon as dead by the visitors 

 to the Aquarium. It is one of the most stupid and lazy fishes of the Medi- 

 terranean, and feeds on fishes frequenting like itself the muddy bottoms 

 of the sea. Its very indifferent flesh is eaten by poor people , its 

 rough skin is used for graters, sheaths for knives, and other purposes. 



The true Hays have a flat body compressed from above, which has 

 on its upper darker surface the eyes and two openings leading to the 

 gills. On the lower paler surface are situated the mouth, the nasal apertures 

 and the gill-slits. They are all deep-sea forms and live on the smaller 

 animals frequenting the bottom of the sea. 



The most interesting form is the Electric Ray, Torpedo (Fig. 65, 

 tank Nr. 12). which was known to the ancients for its curious power of 

 giving electric shocks. Its slimy body is almost circular in shape and 

 contains two large "electric organs". Each of these consists of several 

 hundreds of hexagonal columns of a gelatinous substance, which are sup- 

 plied by a number of branching nerves with curious terminations. These 

 organs give rise to a short and strong electric current when the animal 

 is irritated, its upper surface being positive, the under surface negative; 

 to experience the whole shock, the fish must be touched at the same 

 time on both sides. The shock is not so strong as that of the South 

 American Electric Eel, but is still sufficiently painful in an adult Ray. 

 The shocks become feeblest when repeated frequently. The electric 

 organ is used both defensively by the Torpedo and also for killing or 

 at least numbing its prey. A young specimen is always kept in a small 

 open tank, in front of tank Nr. 10, for visitors to try the electric power 

 of the fish. - - The Electric Ray is one of the most common fishes of 

 the Bay of Naples and in spite of its poor flesh is often brought to 

 market. They bring forth living young ones, 8 14 at a time. The 

 very young embryos have still the shape of sharks and only later on 

 become flattened and disk-shaped. 



Of the other Rays the Skate, Raja (Fig. 69), and the Sting-ray, 

 Trygon (Fig. 62), are found in the Aquarium, but the latter more 

 rarely. The former have a lozenge-shaped body of brown colour, and a 

 tail armed with a number of small spines. They lay their eggs in 

 capsules, which are cast ashore on the beach of the North Sea and are 

 called Skate-barrows. The Sting-rays are of dark violet colour and 

 have a long slender tail. The latter bears a strong spine which can in- 

 flict terrible wounds and is considered poisonous by fishermen. They 

 bring forth living young ones. 



