COPROLITES. 
lOo 
brane, by which it was lined. This evidence 
consists in a series of vascular impressions and 
corrugations on the surface of the Coprolite, 
which it could only have received during its 
passage through the windings of this flat tube.* 
Specimens thus marked are engraved at PI. 1 5 , 
Figs. 3 , 5 , 7 , 10 , 12 , 13 , 14 . 
If we attempt to discover a final cause for 
these curious provisions in the bowels of the 
extinct reptile inhabitants of the seas of a 
former world, we shall find it to be the same 
that explains the existence of a similar structure 
a coprolite, from the inferior chalk, in which this involute 
conical form is well defined. Fig. 4, is the transverse section 
ot another Coprolite from the lias, shewing the manner in which 
the plate coils round itself, till it terminates externally in a 
ro en edge, (at b). , In all the figures the letter b, marks the 
ransverse section of this plate, where it is broken off near the 
termination of its outer coil; the sections at h, shew also the 
sue and form of the flattened passage through the interior of the 
screw. 
A lamina of tenacious plastic substance pressed continually 
forwards from the interior of such a screw, into the cavity of 
att "P '^'thin it, until it 
attained the largest size admitted by its diameter; from this coil 
essive portions would be broken off abruptly, (at b,) and 
^e^cendmg into the cloaca would be thence discharged into the 
sea. 
* These 
bran 'T cannot have been derived from the mem- 
alon ^ ^ inferior large intestine, because they are continued 
becaf ^ surfaces of the inner coils of the Coprolite, which 
permanently covered by its outer coils, in the act of 
'vrirw *1.. • 1 . ■ ... 
4* ^ uy its. uuiei COUS, II 
S lom the spiral tube into this large intestine. 
