194 THE AMERICAN MONTHLY [July, 



ial, I was enabled to isolate quantities of tlie strange, 

 rare, or curiously shaped bodies known as Xanthidia, 

 and which organisms are almost invariably found, 

 when examined with higher powers, in thin flakes of 

 the British flints ; but in this marl they exist in their 

 isolated or free state, and from it they may be removed 

 by selection to any required extent, and can then be 

 viewed in every aspect by suitable manipulation. 



In a reduction of samples of the tough greenish-blue 

 marl clay, I was enabled to find the anchors, shield- 

 plates and wheel-plates of fossil Echinodermata (Holo- 

 thurians) such as characterize the recent or living species 

 of Chirodota and Synapta of the Mediterranean Sea ; 

 also fragments of the ambulacral plates of minute 

 Echini; and minute spines corresponding in form to the 

 recent Gulf species of Spatangus. 



There were also minute Echinodermata (?) having an 

 ornate external glass-like reticular covering which is 

 very fragile and seldom found intact, within whose in- 

 ternal portion is situated a core of sponge-like texture 

 which, while preserving the oblong spheroidal shape, is 

 usually seen divested of the glassy reticular casing. 



There are tri-radiate sponge spicules, characteristic of 

 the marine genus of sponges, Grantia ; stellate spicules, 

 characteristic of the genus Tethya; spicules resembling 

 those of recent Gorgonia ; together with multi-lobate 

 spicules, and, finally, minute ganoid scales of about 

 1-50 inch diameter. 



The minute fossil remains in every case are composed 

 of carbonate of lime, all silicious fossils being absent, as 

 determined by acid tests ; but the foraminifera were in 

 many instances altered or changed to mineral pyrite, or 

 to beautiful casts of a deep green hue. 



Having thus found certain fossil organic remains of 

 Eocene Tertiary age, which have their modern or exist- 



