1845.] 



559 



nearly corresponding witli that of the faluns of Touraine, warmei" 

 than that implied by the polyparian fauna of the crag, and not 

 so tropical as that of the Bordeaux tertiary beds. 



Fossil Echinodermata. 

 In the shelly strata near Coggin's Point, on the James River, 

 Virginia, I found a species of the Spatangus family, of the genus 

 called by Agassiz Amphidetus, which also occurs in the English 

 crag, and in the living fauna of Europe. I also found an 

 Echinus at Williamsburg, and the spines of a second species. My 

 friend. Professor E. Forbes, has favoured me with descriptions of 

 these. 



{^Family Spatangacece.) 

 1. Amphidetus Virginianus Edw. Forbes. 



Amphidetus Virc/iniamis (natural size). 



Body broadly ovate ; elevated and truncate posteriorly. Back oblique ; 

 dorsal impression lanceolate-scutate, area very slightly excavated : ambulacra! 

 spaces broad, triangular, depressed ; interambulacral spaces slightly convex. 

 Anteal furrow broad, shallow ; sides slightly gibbous ; subanal impression 

 broadly obcordate ; post-oral spinous space broadly lanceolate. 



Dimensions of the smaller but more perfect specimens. 

 Lon. unc. 111: Lat. If^; Alt. 1. 



