370 



THE OSTRACODERMS. 





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

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

 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. 



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

 surrounding the exhalent opening of the atrial chamber. 



