60 



Academy of Sciences, eight in the Museum of Comparative Zoology, five 

 in Indiana University, one in Princeton University, twenty-four in the 

 Carnegie Museum. The type of one species, the only known specimen 

 of the species, has been lost. 



A Py!;icli.iin. 



The particular type of catfish underlying all of the Pygidiidae is 

 that of a short eel with a little barbel on the anterior nostril, twin bar- 

 bels at the angle of the mouth, small teeth in bands in the jaws, bunches 

 of spines on the margin of the preopercle and on the opercle, the first 

 dorsal and pectoral rays not spinous, the dorsal placed behind the middle 

 of the body and not followed by an adipose fin. The principal peculi- 

 arities are the twin barbels at the angle of the mouth, the absence of an 

 adipose fin and the development of opercular and interopercular spines — 

 never mind the internal economy. Nobody knows, at least I don't, why 

 there are tivin barbels at the angle of the mouth, or why there is no 

 adipose fin. It is easy to see that the spines on interopercle and opercle 

 are important. They are an adaptation to the insinuating habit and pre- 

 vent an exsinuation if the fish objects to coming out. 



From this basal idea of the Pygidiidae have been developed by addi- 

 tion, subtraction and modification several distinct subfamilies, each with 

 subsidiary basal ideas and a larger or smaller number of radiations. 

 There are the Nematogenyinae with barbels on the chin, remnants really 

 of the more ancient, less specialized cat-fishdom, the Pygidiidae which 

 are the least specialized of the Pygidiidae, and meander over all the 

 mountains of South America, both east and west. The most that can be 

 said of them is that there are a lot of them and that when big enough 

 they are good to eat. Then there are the Stegophilinae with a broad, 

 inferior mouth with innumerable fine teeth in many rows on lips and 



