ACANTHIDIUM PUSILLUM. 43 



base is immediately behind and just below the top of the last branchial slit, so that 

 the hinder canthus of the mouth is half-way between it and the tip of the muzzle. 

 They are larger than the ventral fins, and about the size of the second dorsal fin 

 without its tail. 



The caudal fin is shaped much as in Galeus vulgaris, or Mustelus Icavis, Cuv. ; 

 the upper lobe is obliquely oblong, with a projecting border towards the pointed tip 

 behind, and is much longer than the lower lobe, which is triangular and short. 

 There is no dimple at the root of either lobe. 



The whole fish is of an uniform coal-black, except the tips and edges of the 

 spines and fins, which are pellucid, pale, or whitish ; especially the pectoral fins, 

 the hinder halves of which are nearly colom-less. The whole under side and belly 

 are as black as, or even blacker than, the upper side or back. The iris is of a beautiful 

 golden-green dotted with black : the pupil is of an opaline sea-green, reflecting blue 

 in certain lights. The ball of the eye outside the iris, and the inside edges of the 

 orbits, are of a bluish- white, like the interior of the spiracles, and the smooth cor- 

 ners of the mouth. 



The length of the pectoral fins equals that of the first dorsal fin, or of the ventral 

 fins ; a little exceeding that of the spine of the second dorsal fin ; and is from one 

 eleventh to one twelfth of the whole length. The distance from the tip of the 

 snout or muzzle to the last branchial slit or base of the pectorals is one fourth of 

 the same. The greatest breadth is at the anterior base of the pectorals, and is 

 from one ninth to one tenth of the whole length : it equals or exceeds the greatest 

 height, which is backwarder, at the origin of the first dorsal fin. The longitudinal 

 diameter of the orbits equals or exceeds twice the vertical, and is one nineteenth 

 or one twentieth of the whole length of the fish. The first dorsal fin begins at 

 three eighths, the second dorsal at two thirds the distance from the tip of the muz- 

 zle to the tip of the caudal fin. The distance from the tip of the snout or muzzle 

 to the spiracles is about one seventh of the whole length. The breadth of the top 

 of the head between the eyes, or of the muzzle, exceeds the length of the latter be- 

 fore the eyes, and is about one twelfth of the whole length. The upper lobe of the 

 tail is one fifth of the same, and twice the length of the lower lobe. 



Nothing is known of the habits of this curious little Shark : but, except 

 as limited by size, there is no reason to suppose they disagree with those of 

 others of the tribe. It is captured with a common bait and hook, without 

 confinement to any particular season, though of extremely rare occurrence 

 during any. The individual figured was taken in July, and measured 

 eleven inches and three quarters of an inch in length. Its sex was not 

 particularly noted at the time : but, from tlie figure, it seems to have been 

 a male. It was deposited, with another individual, a female, in the Collec- 

 tion of the Zoological Society of London. 



DESCRIPTION OF TAB. VI. 



Upper right-hand figure. — Teeth of upper and lower jaws in situ. 

 Lower right-hand figure. — Under side of the head. 

 Middle lower figure. — Upper side of the head. 



Left-hand lower figure. — Shows the mode in which the ventral fins are united to the body by their 

 - inner (hinder) margins. This, and the upper right-hand figure, have 

 been taken from a female example. 



All the figures, except that of the teeth, are more or less reduced. 



