166 THE LIAS AMMONITES. 



The profile on the preceding page was drawn by my friend, Mr. R. Etheridge, E.R.S., 

 to illustrate his lecture on the Uhsetic beds of Penarth and Lavernock, delivered at a 

 meeting of the Cardiff 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 planorhis {a, b) occupies the summit of the cliff, and the 

 Ammonite beds consist of dark grey shales, with hard compact limestones ; 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 Cidaris 

 Edwardsii ; above these are beds with Aegoceras planorhis, 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. planorhis, 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 Planorhis zone. They consist of a 

 grey-brownish argillaceous Kmestone with brown shales ; the hmestones are concretionary, 

 and inconstant bands of the rock run through the shales, which measux'e about ten feet. 

 Lima preeciirsor, Quenst., Lima punctata, Sow., Lima pectinoides, Sow., are found in the 

 Upper beds. 



The Ostrea Beds {d, e) consist of alternate layers of clays and limestones. Many of 

 the beds are very fossiliferous, and contain Ostrea liassica. Sow., Modiola minima, Sow., 

 Fleuromya Dunkcri, Terq., Plicatula spinosa, Sow., Hemipedina Bowerbankii, Wr. 



The White Lias series {f—l) 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. Monotis decussata, Awinus concentricus, Moore, 

 Anatina Suessii, Stoip^., Lima prtscursor, Quenst., Fecten pollux, d'Orh., 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 Estheria 

 Brodieana, Jones, and other fossils. 



The Black Shales {m — 'u) form the lower portion of the Contorta-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 Bhceticum, Mer., Axinus 

 cloacinus, Quenst., Gervillia precursor, Quenst., PuUastra arenicola, Strick., Pleuro- 

 phorus angulatus, Moore, Myophoria 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 Saurihthys 

 apicalis, kg., Gyrolepis Alherti, Ag., Hybodus reticulatus, Ag., Acrodus minimus, kg., 



