242 



ated form observable on several pebbles. I have very little doubt of 

 tbese fossils deriving their forms from some lost or unknown species of this 

 genus. 



The first specimen of this kind which attracted my notice, is a flint 

 stone which 1 picked up in the gravel-pits near Hackney-road. This is 

 represented Plate XVI. Fig. 18. The regularity of the transverse striae 

 on the rounded trachea-like body which they compose, and the smooth 

 surface of the valve-like body in which they terminate, gave me at first 

 an idea, not only of its having derived its figure from animal organization, 

 but of its affinity to the barnacle. 



The opinion which I at first formed, received corroboration from dif- 

 ferent specimens which I afterwards met with. In some of these spe- 

 cimens, both the shelly valve and the cartilaginous peduncle are very 

 distinctly defined. The, form of the valve is distinct ; and the membra- 

 neous or cartilaginal part of the peduncle, is apparently, I could almost 

 say obviously, in a corrugated and contracted state ; and the commence- 

 ment of the valve is bordered by a regular and well-defined line: this, 

 indeed, is the case with the specimen here represented. 



At the sale of the Leverian Museum I purchased a specimen, which I 

 suspect to be an English flint, although labelled " A pretty coral, from 

 the East Indies." In this fossil are apparently two distinct peduncular 

 bodies, with their attached valves : one displayed on the upper, and the 

 other turned round on the under surface of the stone. In another spe- 

 cimen, four of these trachea-like bodies appear to have been united in- 

 one central body, by those ends most remote from ^he part which I have 

 named the valve. But whether this fossii has belonged to the genus 

 Anatifa or not, the different states in which the trachea-like bodies are 

 seen, almost demonstrate that it was a part capable of elongation and 

 contraction, as circumstances required. 



It is evident that many of the rugous and striated pebbles have formed 

 parts of this fossiS body: others, undoubtedly, owe their rugae to other 

 fossils ; among which, I believe, the orthoceratites may be mentioned. 



