Crustacea and Zoophyta. 



195 



of clay and lignite, (at Auteuil,) pyrites in great quantities, bones of 

 vertebral animals, whose class has not up to this time (1825) been 

 determined," &c. # 



In 1830, Prevost says that " the remains of reptiles (Crocodiles) 

 and fluviatile shells characterise the plastic clay of the environs of 

 Paris."f 



In the cliff in the southeast part of Chilmark, I found a fragment 

 of bone, which undoubtedly once belonged to a bird. It was hollow 

 and apparently about as much changed as most of the bones at Gay 

 Head. It was so enveloped in the clay that I could have little sus- 

 picion that it was introduced subsequently to the deposition of the 

 clay. 



Crustacea. In the green sand at Gay Head we meet with well 

 characterised specimens of the genus Cancer ; although they are in 

 general much broken ; showing that they originally belonged to a 

 formation which was abraded or destroyed anterior to the production 

 of the green sand. The interior part of the specimen consists of ar- 

 gillaceous matter, probably containing a large proportion of oxide of 

 iron : but the covering of the animal still retains its black shining 

 color, although apparently carbonaceous. The broken state of nearly 

 all the specimens, renders it difficult to determine whether they be- 

 longed to more than one species, although they probably did : and 

 for the same reason I have thought that many drawings would not 

 be of use. (Plate XII. Fig. 31.) 



Fossil crabs have not, I believe, been found in the European plastic 

 clay ; but they occur in the London clay, which is probably only the 

 upper beds of that formation, 



Zoophyta. In the bitummous conglomerate that occurs in rolled 

 masses in the same green sand, I found a branching zoophyte, which 

 may perhaps belong to the genus madrepora ; though its characters are 

 indistinct. 



In the same green sand, and also in the ferruginous sand associ- 

 ated with it, we find numerous concretions whose interior part ap- 

 pears to be compact argillaceous oxide of iron, with the pisiform ore 

 disseminated. Their shape is so exceedingly like that of several of 

 the alcyonia, that I suspect they are petrifactions of those singular 

 animals. They are generally more or less rolled, though not as 



* Ossemens Possiles, Tome 2d, p. 342, 



f Dictionnaire de Historie Naturelle, Art. Terrains, 



