166 
THE LIAS AMMONITES. 
The profile on tlie preceding page was drawn by my friend, Mr. R. Etlieridge, E.R.S., 
to illustrate his lecture on the Rhgetic beds of Penarth and Lavernock, delivered at a 
meeting of the Cardifi" Naturalists' Society in July, 1871. Mr. W. Adams, E.G.S., to 
whom the woodcut belongs, kindly offered the use of the block to illustrate my remarks 
on this section, and for this courteous act I beg to return him my best thanks. 
The zone of Aegoceras pkmorbis {a, b) occupies the summit of the cliff, and the 
Ammonite beds consist of dark grey shales, with hard compact Hmestones ; they are well 
seen at Lavernock, where they occupy the foreshore. The lowest beds consist of fine- 
grained argillaceous limestones and shales, with a few Ammonites and remains of Cidnris 
Edwardsii ; above these are beds with Aegoceras planorbis, Lima pectinoides, Modiola 
Hillana, Pecten textorius. Then follow two beds of limestone, each six inches, without 
fossils, which are capped by two feet of shales crowded with A. planorbis, and inter- 
stratified with a concretionary limestone. The Ammonite beds are about eight feet thick. 
The Lima Shales (c) form the middle portion of the Planorbis zone. They consist of a 
grey-brownish argillaceous limestone with brown shales ; the limestones are concretionary, 
and inconstant bands of the rock run through the shales, which measure about ten feet. 
Lima precursor, Quenst., Lima punctata^ Sow., Lima pectinoides, Sow., are found in the 
Upper beds. 
Tlte Ostrea Beds {d, e) consist of alternate layers of clays and limestones. Many of 
the beds are very fossihferous, and contain Ostrea Uassica, Sow., Modiola minima, Sow., 
Pleuromya Bunkeri, Terq., Plicatula spinosa, Sow., Hemipedina Boicerbankii, Wr. 
The White Lias series (/— /) measures about eighteen feet, and forms the upper portion 
of the zone of Avicula cortorta ; the strata consist of pale brown, arenaceous shales, 
with inconstant bands of hard limestone containing a few fossils. The true White Lias 
limestone of Somersetshire is not found in this locality, but the shells it yields serve to 
identify the beds with that series. Monoiis decussata, Axinus concentricus, Moore, 
Anatina Suessii, Stoipp., Lima pracitrsor, Quemst., Becten pollux, d'Orb., Modiola minima 
Sow., Leda Titei, Moore, Plicatula intusstriata, Emmr., may fairly be correlated with 
the contents of the beds in the Garden Cliff profile (fig. 1, p. 7), which contain ^sz"/^ ma 
Brodieana, Jones, and other fossils. 
The Black Shales {m — u) form the lower portion of the Contorfa-zone, which measures 
twenty-four feet in thickness. These shales contain a fauna special to the beds, remark- 
able for the number of small Mollusca abounding in them. There are two shell beds in 
these shales, both characterised by the presence of innumerable fine large specimens of 
Pecten Valoniensis, Defrance., Avicula contorta. Port., Cardium BhcBticum, Mer., Axinus 
cloacinus, Quenst., Gervillia prceciirsor, Quenst., Pullastra arenicola, Strick., Pleuro- 
phorus angulatus, Moore, Mi/ophoria postera, Quenst. 
The Bone Bed{u), a dark grey grit, or pyritic limestone, containing many small fragments 
of fishes' teeth, bones, and scales, forms the Bone-breccia. I have collected Saurihlhp 
apicalis, kg., Gyrolepis Alberti, Ag., Hybodus reticiilatus, Ag., Acrodus minimus, Ag., 
