VOL. I. | The Evolution of the Catfishes. r3: 
and Ageneiosinz, in which last we observe an approach to the con- 
ditions obtaining in the families with closed air bladders. The meth- 
ods of transition from the Ageneiosinze to the Hypophthalmide has 
been pointed out by us.* 
As is intimated above, the Tachisurinz are the lowest of the liv- 
ing Siluride. The members of this subfamily are mostly marine, 
and from it have, in all probability, been derived the remaining sub- 
families. SSome members of Tachisurine have only the maxillary 
barbels developed, while in others the mental barbels have been 
added. 
From the Tachisurine have unquestionably been derived the 
Callophysinze and Pimelodinz, which differ from each other in 
dentition. Both these subfamilies are neotropical in their distribu- 
tion, the Callophysinz being found in the Amazon and northward, 
the Pimelodinz in the whole region from the La Plata to Mexico. 
One of the chief features modified in passing from the Tachisurinz 
to the Pimelodinz is the space between the anterior and posterior 
nares. In the Pimelodinz the barbels obtain their greatest special- 
ization. The nasal barbels are, however, not developed before the 
Bagrinee are reached. All the North American species belong to 
this subfamily. 
From the Pimelodinz have also been derived the Doradine, in 
which dermal ossifications first make their appearance. + 
In the Doradinz and the succeeding subfamilies of Siluridc the 
Weberian apparatus varies greatly and the whole group seems to be 
in a state of unstable equilibrium. . 
In the Ageneiosine appears for the first time the great reduction 
and splitting into lateral halves of the air bladder. From the 
Ageneiosine were undoubtedly directly derived the Hypoph- 
thalmide.t 
“American Naturalist, July, 1888. 
tMinute plates are noticed along the anterior portion of the lateral line of Platy- 
stomatichthys sturio (Pimelodine). 
!The members of this family were widely separated from the Ageneiosinze by Giin- 
ther, Cope and others on account of the supposed absence of an air bladder and the 
simple anterior vertebre. R. Ramsay Wright proved the presence of an air bladder 
and that the anterior vertebre are codssified, and we have in our MS. Review of 
the Nematognathi followed older authors in placing the genus Hypophthalmus near 
Ageneiosus. Oe - cae : 
