37 



THE OSTRACODERMS. 



, 



FIG. 249. Photograph of a small group of Bothriolepis. The individual, a, after death, came to lie hamal 

 side up, on what was the bottom at that time; its dorsal fin and tail lie in a horizontal plane. Individuals, b andc. 

 died in their natural position; that is, buried in the mud, haemal side down. Their dorsal fins and tail lobes are 

 in a nearly vertical position. 



d. 



\ 



FIG. 250. Photographs of Bothriolepis, seen from the hsmal surface, showing the conspicuous membranous frills 



surrounding the exhalent opening of the atrial chamber. 



