578 



The Class Ostracophori 



City, Colorado. These consist of enormous numbers of small 

 fragments of bones mixed with sand. With these is a portion of 

 the head carapace of a small Ostracophore which has been 

 named by Dr. Walcott Asteraspis desiderata and referred provi- 

 sionally to the family of Aster olepida, which belongs otherwise 

 to the Lower Devonian. 



FIG. 362. Pterichthyodes testudinarius (Agassiz), restored. Lower Devonian 

 Family Asterolepidcp. (After Traquair and others.) 



With these remains are found also scales possibly belonging 

 to a Crossopterygian fish (Eriptychius] . These remains make 

 it evident that the beginning of the fish series lies far earlier 

 than the rocks called Silurian, although fishes in numbers are 

 not elsewhere known from rocks earlier than the Ludlow shales 

 of the Upper Silurian, corresponding nearly to the Niagara 

 period in America. 



In the Ludlow shales we find the next appearance of the 



