282 



SCIENCE. 



[N. S. Vol. IX. No. 217. 



the sclera and choroid. The two layers 

 are not sepai-able. In this respect it ap- 

 proaches the condition in the epigean-eyed 

 member of the family, Chologaster. For 

 other reasons that need not be given here 

 it is quite certain that Typhliclithys is the 



Fig. 2. 



Fig. 3. 



Fig. 2. Dorsal view of the head, with distribution 

 of tactile organs and location of eye. 

 Fig. 3. Ventral view of the head. 



descendant^of a Chologaster. The intensity 

 of coloration^and the structure of the eye 

 are the chief points of difference. The eye 

 of rosoe is but about 1-3 the diameter of that 

 of suhterraneus, measuring .06 mm. or there- 

 about. It is the most degenerate, as distin- 

 guished from undeveloped, vertebrate eye. 

 The point^of importance in the present in- 

 stance is the presence of comparatively enor- 

 mous scleral cartilages.* These have not 

 degenerated in 'proportion to the degenera- 

 tion of the eye and in some cases are several 

 times as long as the eye, projecting far be- 

 yond it or^are puckered to make their dis- 

 proportionate [size fit the vanishing eye. 

 This species is unquestionably descended 

 from a species" with well-developed scleral 

 cartilages, for it is not conceivable that the 

 sclera as found ^ in Chologaster could, by 

 any freak or chance, give rise during de- 

 generation to scleral cartilages, and if it 

 did they would not develop several sizes 



*Kohl mistook the nature of these structures, as 

 he did of every other connected with these eyes, ex- 

 cept the lens and ganglionic cells. 



too large for the eye. At present no known 

 epigean species of the Amblyopsidse pos- 

 sesses scleral cartilages. The ancestry of 

 rosm is hence unknown. Amblyopsis possesses 

 scleral cartilages and the eye of rosce passed 

 through a condition similar to that pos- 

 sessed by Amblyopsis, but the latter species 

 has ventral fins and is hence ruled out as a 

 possible ancestor of rosce. The epigean an- 

 cestry of Amblyopsis is also unknown. The 

 ancestry of Typhlichthys being quite dis- 

 tinct from that of rosoe, the latter species 

 may be referred to a new generic name Trog- 

 lichihys. 



Judging from the degree of degeneration 

 of the eye Troglichthys has lived in caves 

 and done ,without the use of its eyes longer 

 than any other known vertebrate. (Ipnopes 

 being a deep-sea form is not considered.) 

 More than this, rosce is probably the oldest 

 resident in the region it inhabits. 



Since the specimens kindly sent by Mr. 

 Garman,in the course of examination have 

 been reduced to sections, the specimens 

 now in my possession, together with a few 

 sent to the British Museum, all having 

 come from the same cave, may be con- 

 sidered typical. 



In addition to the acknowledgments 

 made before I wish also to thank the offi- 

 cers of the Louisville and Nashville R. E. 

 for transportation to Mammoth Cave. I 

 must especially express my appreciation of 

 the assistance rendei'ed me by Mr. William 

 McDoel, General Manager of the Monon, 

 in enabling me to make explorations in 

 the numerous caves of the Lost River 

 region along his line and to visit caves at 

 greater distances. Mr. H. C. Ganter, the 

 manager of the Mammoth Cave Hotel, not 

 only granted me leave to collect in the 

 cave, but did everything possible to make 

 my trip to this cave successful. 



Cael H. Eigenmann. 



University of Indiana. 



