Here is a superb block of Portland Limestone known as the Roach and containing the high spired snail Aptyxiella portlandica, the ‘Portland screw’, another type of snail and the bivalve shells of Myophorella. The insides of the shells have been filled with sediment to produce internal casts. The gaps are holes where the shells has been dissolved.
The Roach is the very youngest of the Portland Limestone rocks, and the youngest marine jurassic rock in Dorset. The Portland Limestone was deposited in increasingly shallow seas. Directly above the Roach is an eroded surface and a dirt bed or fossil soil.
