384 



REPORT OF THE COMMISSIONER OF FISHERIES. 



Cut 10 indicates the probable relationstiip of the species. The 

 ancestry of the blind lishes is unknown/' At first the group divided 

 into 2, those with and those without ventral fins. TrogUcJithys prob- 

 ably entered the caves first, for its eyes have degenerated farther than 

 any of the species. Ainblyopsis and Typhlichthys probably entered 

 about the same time. CJioJogaster agassisil has only recently entered 

 caves, O. papilUferus is found only in cave springs in southern Illi- 

 nois, and G. cornutus occurs in the southeastern United States in open 

 waters. 



TrogUchthys Typlilichthys 



C. agassizii 



C. papjlliferua 



AmblyopBis 



Entered cave 



Cut 10. — Diagram indicating probable phylogeny of tlie AmblyopsidfC. 

 KEY TO THE GENERA OP AMBLYOPSID.E. 



a. Eyes quite well developed; body more or less colored; ventral fins obsolete; pylo- 

 ric coeca 4 Chologaster. 



aa. Eyes rudimentary and concealed beneath the skin; body colorless; pyloric coeca 

 2 (occasionally 3 in Amhlijopsis) . 

 b. Ventral fins absent. 



c. No scleral cartilages present Typhlichthys. 



cc. Large scleral cartilages present TrofjUclithys. 



hb. A^entral fins present Amblyopsis. 



«Eigenmann, Science, N. S., 1899, IX, 282. 



