MIDDLE LIAS : TRANSITION BED. 
229 
Transition / Grey friable and fossiliferous marl, with 
Bed. \ Am. acutus, A. Holandrei, &c. 
Middle Lias J ^ugmous limestone (as below) - 
N < bandy marl ----- 
(Marlstone). [ Ferri / ginous i imest one. 
FT. IN. 
6 
3 
3 
The following are among the species recorded from the 
Transition Bed, by Messrs. Beesley, Walford, and Beeby 
Thompson : 
Hybodus. 
Ammonites acutus. 
annulatus.* 
caecilia. 
communis. 
crassus. 
Holandrei.* 
Belemnites cylindricus. 
tripartitus. 
Actaeonina ilminsterensis 
Amberleya gaudryana. 
Ataphrus (Turbo) bullatus. 
Bourguetia (Phasianella) turbinata. 
Cerithinella confusum. 
Cerithium ferreum. 
liassicum. 
Cryptaenia expansa. 
consobrina. 
solarioides. 
Pitonnillus linctus. 
Pleurotomaria helicinoides. 
rustica. 
Trochua JSgion. 
rotulus. 
Trochus pethertonensis. 
Turbo cyclostoma. 
Turritella Dunkeri. 
Dentalium elongatum. 
liassicum. 
Astarte subtetragona. 
Voltzi. 
Cardium truncatum. 
Cucullaea hettangiensis. 
Miinsteri. 
Cypricardia cucullata. 
Lima eucharis. 
punctata. 
Macrodon Buckmani. 
Ostrea sportella. 
Pecten dentatus (var. of aequi- 
valvis). 
textorius. 
Plicatula spinosa. 
Unicardium subglobosum. 
Rhynchonella tetrahedra. 
Waldheimia resupinata. 
Tubulipora inconstans. 
Montlivaltia tuberculata. 
Mr. Walford has compared this Transition Bed with the 
Marlstone Pleitrotomaria-bed ou the Dorsetshire coast, t and there 
can be no doubt of the beds being on the same horizon, while the 
overlying basement-beds of the Upper Lias exhibit a close corre- 
spondence throughout the country. Hence this fossiliferous 
horizon may cccur at any locality at the junction of the Middle 
and Upper Lias, although as in the case of other fossil-beds, a 
rich harvest of fossils is only here and there preserved. 
Deposits yielding many Liassic Gasteropods have been noticed 
by C. Moore in South Wales and on the Mendip Hills,J but these 
appear to be of different ages, although some of them have 
yielded species found in the Transition Bed. They have been 
compared with deposits discovered by Deslongchamps, at 
Fontaine-e'toupe-Four and other places in Normandy, where the 
fossiliferous beds occur in rifts and hollows of the Silurian rocks. 
In that country, as in this, accumulations of different Liassic 
stages are preserved, some being evidently equivalent in age to 
* Considerable difficulty appears to exist in separating the forms identified as Am. 
annulatus and A. Holandrei, in the district around Banbury. (See p. 250.) 
| Journ. Northamptonshire Nat. Hist. Soc. 1883, pp. 296, &c. 
J Quart. Journ. Geol. Soc., vol. xxiii. pp. 475, &c. 
Memoire sur la Couche a Leptsena du Lias, 1859. 
