17 



These rays are not extensions of the main limbs of the fin, but are at- 

 tached ; the length of the rays diminishes towards the end of the main 

 limb or principal ray of the fin until it becomes inappreciable ; the ex- 

 tremities of the rays do not lie loosely upon the skin, but the whole fin is 

 covered by a prolongation of the skin, which also covers the principal 

 ray of the fin. In the pectoral fins, the beard of the fin is as long as its 

 ray. In the ventral fins, one-third of the length of the ray is free at the 

 base of the fin ; this then commences very low and remains much lower 

 than in the pectoral fins. In the latter, the beard of the fin external to 

 the ray is three lines broad in its widest part. This kind of formation of 

 the fins, in which the rays arise laterally from a main ray. is quite pecu- 

 liar, and we have no other example of it amongst fish, except in the dor- 

 sal fin of Polypterus" 



The structure of the ventral fins of the singular genus Bregmaceros of 

 Thompson, or Calloptilum of Kichardson, furnishes a much more evident 

 analogy to the pectoral and ventral members of Profopterus than does 

 the structure of the dorsal fin of Polypterus above cited. The ventral 

 fins of Bregmaceros minis of Richardson, formerly described as Callopti- 

 lum mirum, is thus made known by its describer. 



Each ventral fin is " composed of three long, tapering jointed rays, 

 having oblique joints at their bases and transverse ones near the tips. In 

 a small piece of membrane which lies in the axilla of the long rays, there 

 are sixteen short jointed branches, which are grouped so that they may be 

 the tips of three, or perhaps more rays." 



The structure so described appears to be strictly analogous -to that of 

 the pectoral and ventral members of the Protopteri. The genus Bregmaceros 

 is composed of two species found in the Chinese seas ; it belongs to the 

 family of Blennoids, a family which is distinguished partly by the small 

 number of rays in the ventral fins ; the number is rarely more than 

 two or three. The " three long, tapering jointed rays " of Bregmaceros 

 represent the ventral rays of the normal Blennoids, and the branches 

 which lie in the axillae of the inner rays are supernumerary, of which no 

 other group, except the Lepidosirenoids, is known to furnish an example.* 



The Protopterus of Owen and RMnocryptis of Peters have each only a 

 single auricle and ventricle to the heart. This has been positively stated 

 by Owen and Miiller or Peters. 



In the genus Lepidosiren, embracing only elongated species like the type 

 of the genus, the rays have been described as simple, and the heart has 

 been said to have two auricles. 



* From an examination of the figure of the male of Anableps in the eighteenth 

 volume of the " Histoire Naturelle des Poissons," it might be supposed that the 

 anal fin of that fish furnished another analogous instance. Such is not the 

 case; the artist has erroneously represented its structure. And even if the 

 anal rays were attached to the genital production as represented in the figure, 

 the case could scarcely be regarded as analogous to that of the pectoral and 

 ventral members of Protopterus. 



