380 



EEPOET OF THE COMMIHSIONEE OF FISHEEIES. 



shows that while in some species 2 ridges may be coalesced into 1, or 

 an additional ridge may be interpolated, barring such fluctuations, 

 which are occasionally found even on opposite sides in the same spe- 

 cies, the homologue of any ridge is present in all members of the 

 family. The ridges are most conspicuous in the large Ainblyopsis^ 

 though really more highly developed in the smaller Trogllcldhys and 

 Typldlcldhys. In the accompanjang figures homologous ridges bear 

 identical numbers. It will be seen from figures of Ainblyopsis (1, 2, 

 and 3, pi. i), which may be taken as the type, that the ridges form 

 transverse (ridges 1, 2, 3, 4, 6, Y, 9, 10, 12, 13, and other series) or 

 horizontal (ridges 5, 7, 11) series. Over the lateral line canals of the 

 head the ridges are usually at right angles to the canals. On the sides 

 of the head the vertical ridges form more {Anihlyopsis, fig. 1, pi. i, 

 and Chologaster, fig. 1, pi. ii) or less {Typhliclitkys^ fig. 5, pi. i, and 

 especially TrogliclitJiys, fig. i, pi. ii) broken transverse lines. 



The papillpe in a number of the ridges were counted to ascertain 

 whether or not the numbers were uniform in the same and in different 

 species. The results of this count are given in the following table. 

 The similarity is not marked, even in the two specimens of Amhlyopsis. 

 The numbers in the first column of the table correspond to the num- 

 bers of the ridges of the figures. 



Number of pajjillic in tactile ridges. 



