JURASSIC OF THE PARIS BASIN. 



503 



nites cculatus of the variety called A. Bachianus, Oppel, Trigonia 

 spinifera, d'Orb. (Prodr.), and RhynclionelTa Thurmanni. The Tri- 

 gonia is specially noticeable : it has been found by Air. Hudleston at 

 Snainton in Yorkshire, in a quarry belonging to the passage beds 

 above the Lower Calcareous Grit, and named by Dr. Lycett T. snain- 

 tonensis ; but, though never figured by the French geologists, it seems 

 to be abundant in the Ardennes department, and occurs on the same 

 horizon in the Vosges. The Ammonite serves to show how essen- 

 tially Oxfordian these beds still are. Their total thickness is about 

 50 feet. 



Next in the series is the Ferruginous Oolite, which, from its easily 

 recognized mineral character and its rich fauna, has attracted con- 

 siderable attention, and has been constantly used by authors as a 

 term of comparison for beds in other districts. It is of no great 

 thickness, 28 feet being given as its maximum. At Tieil-St.-Kenry it 

 is an earthy limestone with scattered oolitic grains of limonite and 

 crowded with fossils. 



At !Neuvizy almost every thing but the oolite grains has been dis- 

 solved, and these remain as a loose deposit containing ' beekized ' 

 fossils with vacuous interiors. The latter character, however, is 

 exceptional, as the bed may be traced in the former character as far 

 south as Commercy, if not further, a distance of 100 miles. It is, 

 in fact, remarkable for its constancy, especially as compared with the 

 beds above it ; and if a division is to be made in the series in this 

 district on stratigraphical grounds, it is certainly over this that 

 the line must be drawn. From this rock more than 200 species 

 have been recorded in this department, and 190 in the department 

 of the Meuse. In such a fauna one naturally finds representatives 

 of species which are abundant on several horizons ; and one may 

 therefore easily be misled to place it on any horizon that one hap- 

 pens to be most familiar with. Two Ammonites are common, Tiz. 

 A. cordatus and A. Martelli, the latter being the A. plicatilis of 

 d'Orbigny. A form which may belong to the true A. plicatilis occurs 

 in the same beds in the ILeuse department ; and d'Orbigny and Buvig- 

 nier both quote A. perarmatus from this horizon as well as from the 

 beds below. Amongst the Gasteropoda quoted from here, Oerithium 

 muricatum, Littorina muricata, Pseudomelania striata, Chemnitzia 

 heddingtonensis and Bulla elongata are constantly met with in the 

 lower Corallian limestones in England, the Pseudomelania being 

 more characteristic of higher beds. Amongst the Lamellibranchiata, 

 Gryphcea gigantea, Peeten fibrosus, Lima gibbosa, Gervillia avicido- 

 ides, Avicida ezpansa, A. ovalis, A. polyodonta (the same as our 

 A. pteropernoides), Perna quadrata, Jlytilus pectinatus, CucuUcea 

 oblonga, Opis similis, Astarte externa, Tancredia curtansata, Iso- 

 donta Desliayesia, Myacites cUeurtatus, and Pholadomya ovalis are 

 most noticeable as confirming the evidence of the Gasteropoda ; but 

 Pecten vimineus points to a rather higher horizon ; while the presence 

 of Rhy nchonella Thurmanni, and of what is probably P. lacunosa, with 

 abundance of Waldheimia buccidenta and Terebratida Jileyensis, is 

 still in harmony; and finally the echinoderms Millericrinus echinatus. 



