BOLEOSOMA — TESSELLATED DAETERS 



297 



and pectorals and ventrals in active vibration as the pair moved 

 about on the bottom. The eggs are emitted at intervals, and 

 from time to time the female raises a cloud of sand by a vigorous 

 beating with the tail, perhaps for the purpose of covering them. 

 Males in breeding dress have the first dorsal spines more or less 

 swollen, and club-shaped at the tip. 



In studying our collections, wide variation was noticed with 

 respect to the scaly covering of the breast and cheeks, ranging 

 from complete nakedness to complete scaliness of both, and also 

 a considerable variation in robustness of build. While, generally 

 speaking, specimens become more scaly northward and more 

 slender southward, it was not possible to make out, even ap- 

 proximate!}', any line or area of division, either general or local, 

 between the two forms, or to draw any definite dividing line 

 among the variants themselves. This confusion of conditions 

 may be illustrated by the following analysis of a single collection 

 of forty-six specimens (accessions No. 28180) obtained from 

 the north fork of the Vermilion River in Vermilion county 

 June 6, 1901. 



— 28 F 



