of the Island of Trinidad, W I. 39 



channel connecting the bare skin of the muzzle with that of 

 the "fontanelle," belonged to a distinct species, especially as 

 those differences were accompanied by rather smaller size, and 

 longer pectoral spines. On a closer examination of other indi- 

 viduals, we found that the plate varied greatly in size, and 

 that in some, in which the channel hardly existed, it was obso- 

 lete. The pectoral spines were also found to vary in length in 

 specimens that were otherwise identical. We have, therefore, 

 concluded to regard the two specimens with those characters 

 as only forming a variety. 



The Callichthys Isevigatus of Valenciennes appears to have 

 been first figured in the great " Atlas du Voyage dans I'Ame- 

 rique Meridionale" of M. D'Orbigny. As Dr. Kner has already 

 observed, the figure given represents a female. On a com- 

 parison of specimens of the Trinidad fish with that figure, a 

 difference is observed in the form of the operculum, and in the 

 caudal plates ; but as the figure does not aj)pear to have been 

 drawn with much attention to the minute details, we do not 

 venture to separate the two on such evidence, after the positive 

 assertion of Valenciennes. In the figure of the species of 

 Buenos Ayres, the operculum is rejiresented as having the 

 border slightly emarginate, while in the fish of Trinidad, it is 

 nearly straight ; the caudal plates are also represented as being 

 quite angular posteriorly in the figure of D'Orbigny ; in the 

 Trinidad species they are more rounded. Little reliance, how- 

 ever, is to be placed in the latter character, as the caudal plates 

 are subject to considerable variation. Still greater differences 

 are perceptible in the forms of the mastoids, and both pairs of 

 frontals ; but the design of the former appears to have been an 

 error of the draughtsman. 



Subsequently, M. Valenciennes, in his continuation of the 

 "Histoire Naturelle des Poissons," described this species, and 

 referred to the figure in the " Atlas" of M. D'Orbigny. In this 

 work he stated that he had received it from Buenos Ayres, 

 through M. D'Orbigny, and from Trinidad, through M. Robin. 



4 



