Geology of the Harz Mountains. 



225 



which is also chiefly indebted to the Ammonites for its 

 arrangement into the following 8 zones : 



8. Clays with A. Jason, Athleta, Larriberti, gryphcea dilatata, Bel. canalicu- 



latiis. 

 7. Kelloways rock : A. macrocephalus, fimatus, etc. 

 6. Coriibrash, small piece not in place, with. Avicula eckinata. 

 5. Beds with Ostrea Knorrii, Am. feri'ugineus, Parkinsoni, Astarte pulla. 

 4. Clays with brown ironstone : Zone of Am. Parkinsoni, Terebrat. varians, 



Ostrea explanata, Trigonia costata, Pholadomya Murchisoni. 

 3. Zone of Am. coronatus, doubtful. 

 2. Clays with sphserosiderite nodules : Inoceramus polyplocus, Pholadomya 



transversa, etc. 

 1. Dark clays with sphserosiderite nodules : Zone of Am. opalinus, Trigonia 



navis, Nucula Hammeri. 



(3.) The Upper or White Jura contains the Oxford Clay, 

 Coralrag and Kimmeridge beds, and is richly fossiliferous. 

 The various subdivisions of the Jurassic series do not occur 

 with very great persistency, as they often thin out and dis- 

 appear at some places, reappearing again at others. 



The following are the palaeontological groups into which 

 the Upper or White Jura is divided : 



/. Unfossiliferous marly limestone over- 

 laid by cryst. limestone, 30 ft. 



e. Marls with Astarte and Cerithium, 25 

 to 30 ft. 



d. White compact marly limestone, 20 to 

 30 ft. Tereh. subsella, Pecten com- 

 atus, Pholadomya muUicostata, one 

 specimen of Exogyra Virgula. 



c. Dolomitic limestone, 10 to 15 ft., with 

 Pteroceras Oceani, Ponti, etc., etc. 



h. Marls and marly limestone, 20 to 30 

 ft., with Gresslya Saussurii, nuculce- 

 formis, Chemnitzia abbreviata, Natica 

 globosa, dubia, macrostoma, etc. 



a. Marly limestone, 10 ft. Terebratula 

 humeralis. 



4. Kimmeridge 

 group, very ^ 

 fossiliferous. 



Upper . 



Oxford group. ^ 



3. Coralrag. < 



g. Yellow grey marl, 5 ft. , with Exogyra 

 spiralis, Ehynchonella pinguis. 



f. Limestone, 4 ft., with Nerinea {N. 

 visurgis ?). 



e. Oolitic marly limestone, 2 ft. , Exogyra 

 spiralis, Mytilus furcatus. 



d. Dark grey marly limestone, 4 ft. , very 

 fossiliferous. Cidaris crenularis, 

 florigemma, Eh. pinguis, inconstans, 

 Diadema subangnlare. 



c. Grey stratified clay, 2 to 3 ft. 



b. Laminated marly limestone, 3 to 4 ft. 



a. Yellow coarsely oolitic marly limestone 

 and marl, 15 ft. Exogyra lobata, 

 Pecten articulatus, Pleurotomaria 

 suprajuren^is, Terebrat. trigonella. 



VOL. VIII. 



