ORIGIN OF THE BLIND FISHES. 
49 
Anal opening. 
In normal posi- 
tion. 
Forward of pec- 
torals.! 
The same. 
The same. 
Air bladder. 
Present in few 
genera. J 
Present. 
The same. 
The same. 
Scales. 
On body regu- 
larly imbricat- 
ed and loosely 
attached. 
Irregularly ar- 
ranged, firm- 
ly attached 
by being cov- 
ered in great 
part by the 
cuticle. 
The same. 
The same. 
Head with scales 
or naked. ^ 
With scales. 
Naked. 
The same. 
The same. 
Tactile papillce 1| 
on fhe headand 
body. 
Absent. 
Absent. 
Very prominent 
as ridges on 
the head and 
sides of body. 
The same. 
Ventral fins.^ 
Present in most 
genera, absent 
in at least two. 
Absent. 
Absent. 
Present. 
Eyes.* * * § ** 
Well developed in 
all. 
Well developed 
and normal. 
Rudimentary ft 
and of no use. 
The same. 
Habitat. 
Fresh water ; 
brackish water ; 
salt water. 
Limestone wa- 
ter of subter- 
ranean riv- 
ers. Brackish 
water ? 
Limestone wa- 
ter of subter- 
ranean rivers. 
The same. 
Geographical 
Nearly all parts of 
One species in 
Central & south- 
Central and 
range. 
the world; 
subterranean 
streams of S. 
central por- 
tion of the U. 
S.; a 2d spe- 
cies in the So. 
Atl. coast tau- 
na of U. S. 
ern portion of 
subterranean 
fauna of Unit- 
ed States. 
N. central 
portion of 
same. 
From this brief comparison of some of the prominent charac- 
ters of the genera of the Heteropygii with the Cyprinodontes, their 
t Aphrecloderus and Gymnotus, and other genera of distinct orders have this forward 
position of the anus also. 
t The air bladder is in several families present in some species and absent in others. 
§ The presence or absence of scales on the head, or on portions of it, is a generic 
character subject to great variation in many families and quite constant in others. 
li I cannot recall anything but the barbels on the head and jaws of many genera of 
Cyprinoids, Siluroids, Gadoids, etc., etc., that can be said to be tactile organs among 
fishes, with the exception of the fleshy papillae on the head and body of the blind fishes 
of the American and Cuban caves, and the filaments of the fin rays of many fishes 
and the fleshy ventral rays of the Gurnards. 
F Of all fins, the ventrals are the most likely to deviate from their normal structure 
and position. Their presence or absence, as exhibited in many families, and often by 
different ages of the same fish, and the great variation in their position in different 
genera of the sam§ family, render any change in them of either generic, specific, or 
individual character, or simply indicative of age (as they are lost in some adult fishes 
while present in the young, and in others not developed until after the other fins). 
** As I have alluded to the fact, in the first pqrt of this paper, the eyes of fishes are 
no more the constant and unvarying part of the fish structure than the ventral fins, and 
like them are subject to almost every conceivable variation in position in the head, and 
perfection in structure. 
tt The largest specimen I have seen of Typhlichthys, is less than two inches in len gth 
and as the eye of an Amblyopsis of twice the size is not over a 32d of an inch in width 
it must be very small indeed in Typhlichthys, and I confess to not being able to find it 
in an ordinary dissection, assisted only by a good lens. 
MAMMOTH CAVE. 4 
