BuL. U. S. B. v.. 190S. 



Plate CXVIII. 



KiG. 9. — Photograph ol the nest of a horned dace {Semotilus atiomaculadis ), Laken with a reflecting camera 

 and by the aid of a cloth screen used as shown in figure 6, plate cxvi. The reflected image of part of the 

 screen is seen over the right and left parts of the nest. In the upper part of the picture at the right 

 above 5. T. is the sand trail; to the left of this, above P., is the pit. in the bottom of which are large peb- 

 bles; farther to the left, above G.R., is the gravel ridge with its top dressing of fine pebbles. The end 

 of the ridge, its structure of coarse pebbles, is within the pit at the left. 



Fig. 10. — Male and two females of the horned dace {Semotilus atromacnlatits). One female is above at the 

 left, the other behind the male. The head of the male bears four pearl organs. Photographed with a 

 reflecting camera, the fish in an aquarium out of doors. 



