304 



PODABRUS Richardson. 



Contains but two species, as distinct from each other as Cot- 

 topsis is distinct from Cottus. Yet they have this common char- 

 acter of a smooth skin, as Acanthocottus and Cottus have, and 

 teeth on the palatine bones, as is the case with Trachidermis and 

 Cottopsis. On the other hand, Podabrus has slender ventral 

 fins, being composed of two soft rays only, and a small spine, 

 differing in this respect from all other Cottoids. Another pecu- 

 liarity is the crescent-shaped caudal. The two species differ 

 from each other widely by the shape of the head and mouth ; 

 and I should not be at all surprised if more species were found, 

 which would induce their separation into two distinct genera, 

 resting on a combination of characters at present unknown. 



Podabrus comes nearest to the marine tribe ; and this fact 

 gives me much confidence in the track I have followed in the 

 study of the fishes, as it takes into consideration the element in 

 which they live, and their geographical distribution. This shows, 

 moreover, that each family has to be divided into genera accord- 

 ing to characters of a very different value in each. The same 

 may be said of the species ; we cannot start from a uniform 

 principle to ascribe to each their limits. 



Podabrus cottoides Rich. Ichth. of the Voy. Samarang, 1848, 

 p. 13, Tab. I. fig. 1-6. — China Seas ; — Richardson. 



Podabrus centropomus Rich. Ichth. of the Voy. of the Sama- 

 rang, 1848, p. 11, Tab. i. fig. Island of Quelpert ; — 

 Richardson. 



If we now take a general view of the family of true Cottoids, 

 we shall have on one side Acanthocottus, Trachidermis, and 

 Podabrus, that is to say, all which are marine, and on the other, 

 Cottus and Cottopsis, all inhabitants of the fresh waters. 



The genus Acanthocottus, numerous in species, is found in 

 the arctic and temperate zones of both hemispheres, the Pacific 

 excepted. 



The genera Trachidermis and Podabrus, smaller in size, are 

 confined to the Pacific, in the temperate and warm zones. 



