418 The Hon. Mr. Strangways on the 
Where the intermediate bed is argillaceous and charged with 
green earth, as may be seen in the ravines of Crasnoe Celo, the 
limestone in contact with it presents only modifications of the same 
characters. Thus in ascending the ravine of the Golomenca brook 
at CrasnGe Celo, from its mouth, the green sand beds become more 
solid as we ascend, and at last give way to a grey argillaceous 
limestone, sufficiently hard to form steps across the stream, which 
are very convenient to the geological examiner. This argillaceous 
limestone occupies nearly the whole mass of the heights of Crasnoe 
Celo : it abounds in organic remains, of which the following are 
those which are sufficiently distinct to have been named. 
A species of orthoceratite of great size, being sometimes a yard 
in length, and six inches in width. Their outer shell, when 
preserved, which it rarely is, is channelled in the direction of the 
septa of the interior. A good specimen of this is in the cabinet of 
the Mineralogical Society at Petersburg. The casts of the 
siphunculus shew it to be channelled spirally ; the inner shell is 
very thick, and large specimens are often procured ; but the 
termination at either end is always wanting, having probably been 
too thin to resist violence. We are still therefore in doubt whether 
it was curved, or continued in a straight line to its extremity. 
They are seen in great quantities lying in the direction of the beds 
of limestone, but traversed by its perpendicular fissures. 
Two species of trilobite; one, which has been called trilobites 
caudatus , is the most common ; it has a head with two projections 
which have been taken for horns, but are probably prominent eyes 
like those of the lobster, with which this animal appears to have 
had some analogy. It has usually eight, or not more than nine 
plates, disposed in three rows, which in specimens well preserved 
appear to be jointed, part of each being double. It has also a large 
