These are fossilized shells from Thomas Davidson’s “On Some Fossil Brachiopoda,” or “Palaeontological Notes on the Brachiopoda,” from this magazine dedicated to amateur geologists published in 1858.
Amateurs were a lot less amateur in the 1850s, I reckon.
Reading on, we learn that the Rev. T.W. Norwood, of Cheltenham, really loved wandering around North Cave and collecting fossils in a stone he called “ligniferous marl.”
Which would be a great name for a character in something.
I found this thanks to the Biodiversity Heritage Library.