231 



appreciate the sterling value of this work, and commend it to 

 all who wish to extend their knowledge of the formations on 

 which it treats. 



M. de LoEioL gives the collective name terrain Kimmeridien 

 to all the deposits comprised between the "terrain Oxfordien, 

 et les couches de Purbeck," and forms four sub-divisions in 

 the terrain Kimmeridien, — 1° L'etage Portlandien. 2° L'etage 

 Virgulien. 3° L'etage Pterochrien ou Strombien. 4° L'etage 

 Sequanien ou Astartien. These four stages, taken together, 

 correspond very nearly to the Superior Oolite of several authors, 

 and to "l'etage des calcaires du Barrois " of Professor Hebekt, 

 and M. E. Piette. 



L'etage 8equanien consists of a yellow Limestone, with Nerincea 

 Goodhalli, and the sandstones and clays of Wirvigne ; the 

 former rests upon a compact Limestone, with Gidaris florigemma 

 and Phasianella striata; the Nerinsean Limestone contains a 

 great abundance of N. Goodhalli and Terebratula humeralis. 

 The Sandstone of Wirvigne contains a great number of Echinidse, 

 as Pseudodiadema mamillanum and Pygurus Royerianus. Ostrea 

 virgula appears here for the first time. 



L'etage Pterochrien consists of thin beds of argillaceous Lime- 

 stones, having other coloured bands interstratified with them, 

 and containing Pholadomya hortulana, Ceromya, and Pinna 

 granulata. 



L'etage Virgulien, with L'etage Portlandien, constitute the 

 entire escarpment of the Jurassic cliffs of the Bas-Boulonais ; 

 the former consists of an intercalation of dark-coloured clays, 

 limestones, sands, and sandstone, with Ammonites longispinus, 

 Trigonia variegata, Trigonia Bigauxiana, Ostrea virgula, Phola- 

 domga aeuticostata, and has a thickness of 80 metres. 



L'etage Portlandien admits of a three-fold division, — the 1st, 

 or inferior stage, from 15 to 20 metres in thickness, consisting 

 of sands and sandstones, with Ammonites gigas, Natica Marcou- 

 sana, and Perna rugosa ; they are all well exposed in the Cap 

 de la Creche and in the railway cutting at Terlincthun; the 

 fossil shells are numerous, as Trigonia Micheloti, Tr. Barrensis, 

 Tr. Boloniensis, Mytilus Morrisii, Ostrea virgula, Astropecten 

 Loriolii, and Hemicidaris Purbeckensis. 



