3156 Bulletin ^7, United States National Museum. 



rarely absent. Fully grown males are scarce, a large catch consisting 

 mostly of females and young. 



Xiphophorns monteznmw, is distinguished from the other known species 

 of the genus by having 1 anal rays, the scales with conspicuous dark 

 edges, a largo brown caudal spot, and the caudal appendage not sword- 

 shaped, but with its end enlarged and blunt. (Jordan & Suyder.) 



Known only from Rio Verde, near Rascon, San Luis Potosi, Mexico. 

 (Type, a male, No. 6145, L. S. Jr. Univ. Mus. Coll. J. O. Snyder. ) 



XipJiophorus montezumce, JORDAN & SNYDER, Bull. U. S. Fish Com. 1899 (1900), 131, 

 Rio Verde, near Rascon, Mexico. 



Page 702. The recent studies of the eyes of American blind fishes by 

 Dr. C. H. Eigeumann have shown that the species occurring in the caves 

 of southwestern Missouri which has usually been identified as TyphUchthys 

 stibterraneus, Girard, but which Dr. Eigenmann described as a new species 

 under the name Typlilichthys rosm (p. 2835), has had an ancestry quite 

 distinct from that of Typhlichthys. It therefore is generically distinct 

 from Typhlichtkys, and has been made the type of the new genus Troylich- 

 tJiys by Eigenmaiin. 



322 (a). TROGLICHTHYS, Eigenmann. 



Troglichthys, EIGEXMAXN, Science, X. S., Vol. ix, Xo. 217, p. 282, Feb. 24, 1899 (rosce). 



Scleral cartilages present, pigment in the pigment epithelium; vitreal 

 cavity obliterated, no hyaloid membrane; pupil closed, some of the eye 

 muscles developed; no outer reticular layer; outer and inner nuclear 

 layers merged into one; eye in adult not connected with the brain; pig- 

 ment epithelium developed on the distal face of the eye, rarely over the 

 sides and back; no cones; nuclear layers mere vestiges ; ganglionic layer 

 restricted to the anterior face of the eye just within the pigmented 

 epithelium. Maximum diameter of eye about 85//. No ventral fins. 

 (Tp(oyhrj, cavern; i% f Jv:, lish.) 



The genera an 1 species of Amblyopsidae may be determined by the fol- 

 lowing key (from Eigeninanii), based largely on the character of the eyes: 



a. Vitreous body and lens normal, the eye functional; no scleral cartilages; eye perma- 

 nently connected with the brain by the optic nerve ; eye muscles normal ; no 

 optic fiber layer. Minimum diameter of the ej-e O.TOO.u. Xo ventral tins. 



CHOLOGASTER, 321. 



b. Eye in adult more than 1 mm. in longitudinal diameter; lens over 0.5 mm. in diam- 



eter; retina very simple, its maximum thickness 83.5/u. in the old; the outer 



and inner nuclear layers consisting of a single series of cells each ; the gan 



glionic layer of isolated cells. Maximum thickness of the outer nuclear 



layer 5ju, of the inner nuclear layer 8,<x. CORXCTUS, 1044. 



bl>. Eye in adult less than 1 mm. in longitudinal diameter; lens less than 4 mm.; 



outer nuclear layer composed of at least 2 layers of cells; inner nuclear 



layer of at least 3 layers of cells, the former at least lOju. thick, the latter at 



least 18 M . 



c. Pigment epithelium 65.u thick in the middle-aged, 102,a in the old. 



PAPILLIFERUS, 1046. 



cc. Pigment 49^ thick in the middle-aged, 74,u. in the old ; 24 to 30 per cent thinner 

 than in papilliferus ; eye smaller. AGASSIZII, 1045. 



