1 62 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



II. History and Relationships of Species. 



The one new species, Schizaster Le Contei, PL XXI, fig. 

 I, here added to the list of forms known from Middle Cal- 

 ifornia, is of special interest, as it occurs in the lowest Ter- 

 tiary, Martinez, and represents a family not known in this 

 region later than that time. It seems to be confined to 

 the Martinez and serves as a characteristic fossil of that 

 formation. 



The Tejon formation, resting on the Martinez and form- 

 ing the uppser portion of the Eocene on the Pacific Coast, 

 is not known to contain any echinoid remains, though they 

 may be expected to appear in later collections. 



In the Miocene the Clypeastridce begin and they continue 

 as the only representatives of the class up to the beginning 

 of the Recent period.^ The oldest certainly known form of 

 this family is Clypeaster (?) Brewerianus^ PI. XXI, fig. 2, of 

 the Contra Costa County Miocene. This species is small 

 and shows no specialized characters, and, as will be shown 

 later, is probably the ancestor of some of the younger forms. 



In what have been considered the lowest beds of the San 

 Pablo formation, immediately overlying the Miocene of 

 Contra Costa County, is found the oldest species of the 

 more specialized division of the Clypeastridas included in 

 the subfamily Scutellinas. This species, Sciitella Gahhi^ 

 PI. XXII, fig. 5, is structurally considerably removed from 

 Clyf easier Brewerianus and it is doubtful whether they are 

 nearly related. The Scntella is probably an immigrant 

 from some other region. 



Immediately above the Scntella beds the characteristic 

 San Pablo species, Astrodapsts tmnidus, PL XXI, fig. 3, 

 is very abundant. The Scntella and A . tmnidus have been 



1 A new species of regular sea-urchin has recently been discovered by Dr. H. W. Fair- 

 banks in the Miocene of southern California. vSuch forms may also have been repre- 

 sented in middle California, but as the middle and southern portions of the State show 

 in general quite different faunas, we cannot from this occurrence draw any definite 

 conclusions as to the existence of such forms farther north. 



"^ Echinarachnius Brewerianus of earlier writers. 



'^ Clypeaster Gabbi of earlier writers. 



