SKATE. 91 



fish are, from the snout to the mouth one part to three and 

 three quarters of its breadth, and less than one fifth of its 

 whole length. The males, like the Sharks, are distinguished 

 by claspers attached to the ventral fins, but they are larger 

 in proportion to the bulk of the fish. The colour of the 

 upper parts is dusky or grey, variously mottled; and in the 

 younger examples the tail is marked with rings of colour. It 

 often reaches the weight of a hundred pounds, and would 

 scarcely be thought extraordinary if of double that magnitude. 

 I have thought it proper, in my introductory remarks on 

 the newly-named genus, Balis, to direct attention to the 

 conspicuous mucous glands which characterize this division 

 of the great family of Plagiostomes ; and Monro has thought 

 them worthy of a separate chapter in his work on the 

 "Physiology of Fishes." "In the Skate," says he, "numerous 

 orifices, placed pretty regularly over the surface, have been 

 observed by Steno to discharge the slimy matter. With 

 respect to these last I have remarked some memorable circum- 

 stances. First, I have discovered one very elegant serpentine 

 canal between the skin and muscles, at the sides of the five 

 apertures into the gills. Further forwards it svirrounds the 

 nostrils, then it passes from the under to the upper part of 

 the upper jaw, where it runs backwards as far as the eyes. 

 From the principal part of this duct in the under side or 

 belly of the fish, there are not above six or eight outlets; 

 but from the upper part near the eyes there are uj)wards of 

 thirty small ducts sent off", which open upon the surface of 

 the skin. The liquor discharged from these has nearly the 

 same degree of viscidity as the synovia in man. But besides 

 the very picturesque duct I have been describing, I have 

 remarked on each side of the fish, a little further forwards 

 than the foremost of the five breathing holes, a central part, 

 from which a prodigious number of ducts issue, to terminate 

 on almost the whole surface of the skin, excepting only the 

 snout or upper jaw. At these centres all the ducts are shut; 

 and in their course they have no communication with each 

 other. In these two central parts, or on the beginning of 

 the mucous ducts, a pair of nerves, nearly as large as the 

 optic, terminate; and, which is a curious circumstance with 

 respect to them, they are white and opaque in their course 



