OAVE FISHES OF NORTH AMERICA. 391 
TROGLICHTEYS Eigenmann. 
Troglichthys Eigenmann, Science, N. 8., TX, 1899, 280 (rose). 
This genus is very much like 7ypAlichthys, from which it differs in 
the structure of the eyes, especially by the presence of large scleral 
cartilages. 
Troglichthys rose (EKigenmann). Pl. IV, fig. 1. 
Body similar to that of Typhlichthys, but slightly heavier. Depth 
4,5 in head; head 8, depressed; mouth oblique, lower jaw slightly pro- 
jecting; snout rounded; eye not visible, considerably smaller than that 
of Typhlichthys; gill membranes joined to isthmus; head and body 
well supplied with tactile ridges; fins similar to those of Zyphlichthys; 
dorsal with 8 rays; anal 8; pyloric ceca 2. Color in life, yellowish - 
pink, no dark spots anywhere. Length 1.167 in. 
T. rose inhabits subterranean waters in southern Missouri, north- 
ern Arkansas, and probably eastern Kansas. The type specimens are 
from the cavesat Sarcoxie, Mo. It is this species whose habits Doctor 
Garman and Miss Hoppin have studied. 
The following is quoted from Doctor Kigenmann in Science, N. S., 
IX, 1889, 280. ‘‘On the surface the specimens very closely resemble 
Typhlichthys subterraneus from the Mammoth Cave. * * * It is, 
however, quite evident from a study of their eyes that we have to deal 
here with a case of convergence of two distinct forms. They have 
converged because of the similarity of their environment, and especially 
owing to the absence of those elements in their environment that lead 
to internal protective adaptation. * * * The eye of Zyphlichthys 
is surrounded by a very thin layer of tissue representing the sclera 
and choroid. The two layers are not separable. In this respect it 
approaches the condition in the epigeean-eyed member of the family, 
Chologaster. The eye of Troglichthys rosx is but about one-third the 
diameter of that of Zyphlichthys subterraneus, measuring 0.06 mm. or 
thereabouts. It is the most degenerate, as distinguished frem the 
undeveloped vertebrate eye. The point of importance * * * is the 
presence of comparatively enormous scleral cartilages. * * * This 
species is unquestionably descended from a species with well-developed 
scleral cartilages, for it is not conceivable that the sclera as found in 
Chologasier could, by any freak or chance, give rise during degenera- 
tion to scleral cartilages, and if they did they would not have devel- 
oped several sizes too large for theeye. At present no known epigean 
species of the Amblyopsidx possesses scleral cartilages and the eye of 
rose passes through a condition similar to that possessed by Amblyop- 
sis, but the latter species has ventral fins, and is hence ruled out as a 
possible ancestor of rose. * * * Judging from the degree of degen- 
eration of the eye, Zroglichthys has lived in caves and done without 
the use of its eyes longer than any other known vertebrate.” 
