
- Parr IIL Szor.ii.§2] JURASSIC. 795 
thinning away or disappearing in the inland counties. This zone is 
fairly comparable with the “ Virgulian group” of foreign authors. 
(a.) Lower Kimmeridgian, blue or sandy clay with calcareous “‘doggers,’ repre- 
senting the “Astartian group” of foreign geologists, This is the 
great repository of the fossils of this group.! 
7 
_ Among the more common fossils are numerous foraminifera (Pulvulina 
pulchella; Robulina Miinstert), also Serpula tetragona, Discina latissima, 
Hxogyra virgula (Fig. 373), H. nana, Thracia depressa, Corbula Deshayesia, 
Cardium striatulum (Fig. 373), Belemnites nitidus, Ammonites biplex, A. 
decipiens, A. Berryert, A. serratus. Numerous remains of fishes have 
been obtained, also reptiles of the genera Ischyosaurus, Megalosaurus, 
Ceieosaurus, Plesiosaurus (12 species), Pliosaurus (5), Ichthyosaurus (9), 
Teleosaurus, Steneosaurus, Dakosaurus, and Goniopholis. 
(2.) Portlandian, so named from the Isle of Portland, where it is 
typically developed. This group, resting directly on the Kimmeridge 
clay, consists of two divisions, the Portland Sand and Portland Stone. 
At Portland, according to Mr. J. F. Blake, it presents the following 
succession of beds in descending order :? 
( Shell limestone (Roach), containing Cerithium Portlandicum (very abund- 
ant), Sowerbya Duket, Buccinum naticoides. 
“Whit bed” — Calcareous Freestone, the well-known Portland stone 
(Ammonites giganteus), 
“ Curf,” another calcareous building stone (Ostrea solitaria). 
“ Base-bed,” a building stone like the whit bed, but containing irregular 
bands of flint. 
Limestone, “ Trigonia bed” (Trigonia gibbosa (Fig. 373), Perna mytiloides). 
4 Bed (8 feet) consisting of solid flint in the upper and rubbly limestone in 
the lower part. 
Band (6 feet) containing numerous flints (Serpula gordialis, Ostrea multi- 
formis). 
Thick series of layers of flints irregularly spaced (Ammonites boloniensis, 
Trigonia gibbosa, T. incurva). 
Shell bed abounding in small oysters and serpulee (Ammonites pseudo- 
gigas, A. triplex, Pleurotomaria rugata, P. Rozeti, Cardiwm dissimile 
{ (Hig. 373), Trigonia gibbosa, T. incurva, Pleuromya telling). 
(Stiff blue marl without fossils (12 to 14 feet). 
Liver-coloured marl and sand with nodules and batids of cement stone— 
26 feet (Mytilus autisstodorensis, Pecten solidus, Cyprina implicata; 
| Ammonites biplea, &c.). 
Oyster bed (7 feet) composed of Hxogyra bruntrutana. ' 
Portland Stone. 

Yellow sandy beds—-10 feet (Cyprina implicata, A7éa). 
Sandy marl (at least 30 feet) passing down into Kimmeridge clay (Aim- 
monites biplea, Lima boloniensis, Pecten Morini, Avicula octavia, Trigonia 
incurva, T. muricata, T. Pellati, Rhynchonella Portlandica, Discina 
\ Humphriesiana). 
Portland Sand. 
Among Portlandian fossils a single species of coral (Lsastrzea oblonga) 
occurs; echinoderms are scarce (Acrosalenia Konigi, &c.), there are also 
few brachiopods. ‘he most abundant fossils are lamellibranchs, the 
best represented genera being, Trigonia, Astarte, Mytilus, Pecten, Lima, 
Perna, Ostrea, Cyprina, Lucina, Cardium, Pleuromya. Eight species of 
Ammonite occur (A. giganteus, pseudogigas, boloniensis, triplicatus, biples, 
pectinatus, Bleicheri (?), Boisdint). Fish are represented by two genera 
(Chimera and Pycnodus), and some of the older Jurassic saurian genera 
1 J, F. Blake On the Kimmeridge Clay of England. Q. J. Geol. Soc. xxxi. 
2 Q. J. Geol. Soc. xxxvi. p. 189. 
