326 



ICHTHYOLOGY. 



Classifica- fins forming a discoid or subrhomboidal body, with an ap- 

 tion — pended tail, which in the lihinohatidce is fleshy and taper- 

 Kays. jj^g^ jji^j j^ j],g JlaiidcE, Tri/gonidcE, and some other groups, 



^"V~^ is cartilaginous and slender, and sometimes elongated like 

 the thong of a whip. In some a narrow lancet-shaped spine 

 placed erect on the dorsal surface of this whip-like tail, with 

 its cutting edges turned sideways, proves a dangerous offen- 

 sive weapon, which the fish can use with great effect. The 

 cartilaginous scapular arch is complete on the ventral sur- 

 face, and running forwards at some distance, laterally from 

 the skull in a crescentic tapering point, gives support to 

 the long, jointed cartilaginous rays of the pectoral. In the 

 space between the hinder horns of the scapulo-coracoid 

 cartilages laterally, and the pelvic cartilages behind, lie the 

 abdominal viscera; whilethe branchial apparatus and vascular 

 centres occupy the posterior part of the spaces between the 

 anterior cornua of the scapular arch and the narrow skull. 

 On looking at the skeleton of a Skate, it will be seen that 

 the skull is comparatively narrow ; that the cartilages sup- 

 porting the branchial apparatus stand out like wings behind, 

 and those on which the eyes are placed also project laterally, 

 exactly like the prominent orbits of the Zijgcena, but that 

 this lateral prominence is concealed in the entire Skate by 

 being inclosed between the points of the pectorals. Ante- 

 riorly the skull is completed by a tapering cartilage whose 

 tip supports the end of the snout. In the TorpedinidfB, a 

 cellular galvanic battery fills up the wide spaces between 

 the skull cartilages and the front horns of the pectorals. 

 Recently a homologous apparatus, but much smaller and 

 merely rudimentary, has been discovered in the ordinary 

 Skates — an indication seemingly of a general plan of struc- 

 ture in the members of the group, irrespective of function, 

 which it has pleased the Great Architect of the Universe 

 to give. 



Except in the genera Anacanthiis, Aetobates, and Mylio- 

 bcttes, we are not aware of any species of Ray that is com- 

 mon to both the Atlantic and Pacific districts of the ocean, 

 but several exist both in the Mediterranean and North seas. 

 Anacanthus africamis has been taken both in the Red Sea 

 and in the Gulf of Guinea. Mi/liohates Nieuhojii exists in 

 the Mediterranean, and in the Indian and Australian seas, 

 and Aetobates naritiari frequents the coasts of Brazil, as 

 well as the Red Sea and the Indian Ocean. Of the range 

 of species, however, we are not prepared to speak with con- 

 fidence. What is at present known on the subject rests 

 chiefly on specimens in the European museums, examined 

 by Miiller and Henle, whose work on the Plagiostomi is 

 the only one professing to include all the known species. 

 The great advances that ichtliyology has made since the 

 publication of that work, and the attention now paid to ana- 

 tomical structure in the definitions of species, will enable 

 future ichthyologists to enter on the inquiry of distribution 

 of species with great advantages. The Rays found on the 

 British coasts are Torpedo marmnrata, and T. nobiliana, of 

 only occasional occurrence, and much more abundant in 

 the Mediterranean ; Raia rudiihi, R. cfarata, R. radiata, 

 R. batis, R. marginata, R. fulloiiica, R. o.ri/rliyncha, R. 

 microcellata, R. intermedia, R.li/i(ea,Sind R. acus; Cepha- 

 loptern Gioriia, Myliohati.i aqui/a, and Tri/gon pastinaca. 

 Some of these are of daily occurrence in our markets, as 

 the R. batis, Blue or Grey Skate, Tinker or True Skate. 

 The R. oxi/rhiticha (L.), or miraleta (Yarr. Ed. 2'^'^), 

 Homelyn, Spotted Ray, or Sand Ray, is stated by Mr 

 Yarrell to be one of the two commonest Skates brought to 

 the London market ; the other being the R. clarata, 

 Thornback, Young Maidens, or Maiclen Skate. Unlike 

 most fish, the Skate improves by keeping several days, being 

 hard and tough when cooked soon after it is caught. It is 

 one of the fish that the fishmongers are in the habit of 

 crimping. Figure 7, p. 123, represents the Raia Lemprieri, 

 an Australian Skate, which somewhat resembles the Ho- 



melyn of our own coasts in general form, and fig. 136 shows Classifica- 

 the under surface of its head. 



Some of the Cephalopteridm attain an enormous size. 

 One mentioned by Risso, taken off Messina, weighed 12o0 

 lbs.; the male is usually the smallest. Of a pair spoken of 

 by this author, the female was first taken, and the male re- 

 mained hovering about the boat for three days, and was 

 afterwards found floating dead on the surface. But the 

 size here spoken of is greatly surpassed by other fishes of 

 this order, which have been but imperfecdy described, such 

 as the Raia Banksii of Lacepede, referred with doubt to 

 the genus Ceratoptera by Miiller and Henle. A fish of this 

 kind taken at Barbadoes required seven yoke of oxen to 

 draw it. A sketch of another, which was said to be 20 feet 

 long, was sent to Lacepede; and Levaillant, in his second 

 voyage to Africa, speaks of one which swam round the ves- 

 sel, and appeared to be about 25 feet long and 30 wide. 

 Sonnini also mentions one which seemed to him (o be longer 

 and wider than the ship in which he was sailing. 



The Torpedinidce all jiossess electric organs, and it is the 

 space occupied by these batteries that gives the round or 

 truncated outline to the fore part of the fish. The batteries 

 lie one on each side of the head, bounded behind by the sca- 

 pular arch, and laterally by the anterior crescentic tips of the 

 pectoral fins. They consist of a congeries of vertical prisms, 

 whose ends are in contact with the integuments above and 

 below ; and each prism is subdivided by delicate transverse 

 septa, forming cells which contain a fluid, and are lined 

 widiin by an epithelium of nucleated corpuscles. Between 

 this epithelium and the transverse plates and walls of the 

 prism, there is a layer of tissue, on which the extreme 

 twigs of the nerves and vessels ramify. Hunter counted 

 470 prisms in each battery of the Torpedo galvani, and de- 

 monstrated the enormous supply of nervous matter which 

 they receive. Each organ receives one branch of the tri- 

 geminal nerve, and four branches of the vagal nerve, the 

 former and the three anterior branches of the latter being 

 each as thick as the spinal chord. The fish gives the elec- 

 tric shock voluntarily, when excited to do so in self-defence, 

 or when roused to kill its prey ; but to receive the shock 

 the object must complete the galvanic circuit by communi- 

 cating with the Torpedo at two distinct points, either di- 

 rectly or through the medium of some conducting body. 

 The shock received on handling the fish is described as too 

 strong to be willingly encountered a second time, and it is 

 said that a painful sensation may be produced by a discharge 

 conveyed through the medium of a stream of water. 



Sub-Order II.— RALS;. 



Plagiostomi, with flat bodies, spout-holes. Five slit-like gill- 

 openings on the ventral aspect before the ventrals and under the 

 pectorals. Eyes and spout-holes on the dorsal aspect. A complete 

 scapular arch. Naso-pectoral cartilages. No eyelid, or an adnata 

 upper one only. 



ANALYTICAL TABLE OF THE RAI^ (Dum.) 



Tail long, and 



Very thick at the root. 

 Snout prolonged. 



Set laterally with teeth Pristis. 



With even, thin, smooth edges Rhinobates. 



Snout rounded, smooth Rbina. 



Slender 



Dorsals two, caudal ; disk rhomboidal RaJA. 



Dorsal single or wanting. 



Eyes on the dorsal aspect. 



Teeth small ; tail spiniferous Trvgon. 



Teeth broad, flat, grinders MVLIOBATES. 



Eyes lateral; head truncated, horned.. CEPHALOPTERtJS. 

 Tail short ; body smooth; electric organs visible Torpedo. 



