JUltASSIC FAUNA AND FLORA. 15 
in the clays and earthy limestones, and in the sandy strata, but 
rarely in the false-bedded oolitic rocks. The Nautilus is also 
found. 
The Gasteropods and Lamellibranchs comprise mostly genera 
now living. The Gasteropods include Natica, Plcurotomaria, 
Trochus, Turbo, Chcrnnitzia, Ccrithium, Nerita, Actceonina, 
Littorina, Turritella, Patella, and the extinct Alaria, Bourguctia, 
Amberleya and Nerincea : they are most abundant in the lime- 
stone?. 
The Lamellibranchs include Area, Astarte, Avicula. Ceromva 
*/ * 
Ct/pricardia, Exogyra, Gervillia, Goniomya, Gressiya, Gryphcea, 
Hinnites, Inoceramiis, Lima, Modiola, Monotis, Myacites, Ostrea, 
Pccten, Perna, Pkoladomya, Thracia, Trigonia, and Unicardium. 
In several instance the colour-markings of Mollusca and 
Brachiopoda have been preserved. This has been noticed in 
species of Natica, Nerita, Cyprina, Hinnites. Pecten. Terebratula, 
and Waldhcimia* The occurrence has been noted of a "pearl-like 
body " on a specimen .of Gryphcea, derived probably from the 
Oxford Clay, but found in the Glacial Drift of Muswell Hill, 
Hornsey.f 
Species of Ostrea and Gryphcea often constitute conspicuous 
bands and sometitnes thick beds. Thus in the Lower Lias the 
basement-beds are* frequently crowded with specimens of O street 
liassiea, and at a higher horizon on the Glamorganshire coast, and 
especially at Fretherne in Gloucestershire, there are bands crowded 
with Gryphcea arcuata. It is interesting to note that similar 
bands occur as far north as Raa.-ay and Broadford in Skye. In 
the Inferior Oolite of the neighbourhood of Cheltenham and 
Stroud, there is the Gryphite Grit, largely made up of specimens 
of Gryphcea sublobata. Varieties of Ostrea acuminata and O. 
Soiverbyi form a thick band in the Fullers Earth near Weymouth. 
O. Sowcrbyi is abundant in the Forest Marble, and O. subrugulosa 
in the Great Oolite clays. Gryphcea bilobata is characteristic of 
the Kellaways Rock, and large forms of Gryphcea dilatata 
are prevalent at the top of the Oxford Clay. Ostrea deltoidea 
forms bands in the iron-ore of Westbury in Wiltshire at the top 
of the Corallian rocks, and also at the base of the Ki me ridge Clav. 
In the Lower Portland Beds at Swindon there is a marked laver 
largely made up of Exogyra bruntrutana, and in the Purbeck Beds 
of Dorsetshire and Wiltshire there is the remarkable Cinder Bed, 
formed mainly of Ostrea distorta. 
Some of the species of Lamellibranchs have a wide runo-e : 
anfong these ma}' be mentioned, Lima duplicata, L. pcctiniformis , 
Avicula incequivalvis, Pecten demissus, P, lens^ &c. 
Brachiopoda are exceedingly abundant in the calcareous strata, 
and like the oysters there are species that occur gregariously, and 
* Lycett, Ann. Nat. Hist., 1850, p. 423 ; J. F. Blake, Quart. Journ. Geol. Soc., 
vol. xxxvi., p. 201 ; G. F. Whidborne, Ibid., vol. xxxix., p. 499; E. Wilson, Geol. 
Mag., 1891, p. 458. 
f Morris, Ann. Nat. Hist., ser. 2, vol. viii., plate 4, fig. 16. 
