PLATE 17, 18. 
tain any, is either wholly detached, or left adhering to such 
parts of the matrix, as have escaped the effects of the air 
and rain. I have met with some very perfect specimens of 
this kind, in a wall between Sheldon and Ashford, on the 
right hand side of the road, about half a mile from the first 
mentioned village. 
This petrifaction Is usually considered as the remains of 
the Madrepora c<espitosa of Linne. Two varieties of it are 
found in this county : in one the branches are somewhat 
clavated, growing thicker toward the tops: the other has 
the branches perfectly cylindric and equal. 
Fig. 1 . Is a specimen of the first variety. In a large mass 
of limestone : the coral itself consists of quartz and chert. 
A drawing of the other variety will be given in the course 
of the work. 
FIG. 2, 3. 
► ERISMOLITHUS Tubiporites ? (radialus) aggre- 
gatus, dissepimentis transversis undatim radiato-stria- 
tis tubos erectos striatos connectentibus. S. p. 
Fossil coral. The original a Tubipore f Aggregate. Stirps 
tube-like, distant, erect, striated, parallel, and connected 
by transverse dissepiments or partitions. The surface of 
H 
