LOWER LIAS FOSSILS. 45 
The more abundant and characteristic fossils of the several 
zones in the Lower Lias may be grouped as follows, and we 
may look to the prevalence of the index-species to mark the 
particular zone : 
Zone of AMMONITES PLANORBIS (Fig. 12). 
Ammonites Johnstoni. 
Avicula cygnipes (Fig. 34). 
Lima gigantea (small examples) (Fig. 28). 
Modiola minima (Fig. 32). 
Ostrea liassica. 
multicostata. 
Pecten pollux. 
Pleuromya crowcombeia^ (Fig. 33). 
Cidaris Edwardsi. 
Hemipedina (several sp.). 
Zones of AMMONITES ANGULATUS (Fig. 13), A. BUCKLANDI, 
(Fig. 14), A. SEMICOSTATUS, and A. TURNERI. 
Ammonites bisulcatus. 
Bonnardi. 
Charmassei. 
Conybearei. 
rotiformis. 
sauzeanus. 
Belemnites acutus, 
infundibulum. 
Nautilus striatus. 
Crypta3nia rotellteformis. 
Pleurotomaria jinglica (Fig. 27). 
Avicula inaequivalvis (sinemuriensis). 
Cardinia concinna. 
- Listeri (Fig. 30). 
- var ovalis. 
Gryphspa arcuata (incur va) (Fig. 35). 
Lima gigantea (large specimens from 3 to 10 in. 
across) (Fig. 28). 
Herrnanni. 
- punctata. 
Modiola hillana. 
Myoconcha psilonoti. 
Pecten calvus. 
- lunula r is (iiasirms). 
textorius. 
Pholadomya ambigua. 
glabra. 
Pinna Hartmanni. 
Pleuromya crassa. 
Unicardium cardioides. 
Rhynchonella calcicosta. 
Spiriferina Walcotti (Fig. 36). 
Pentacrinus basaltiformis (Fig. 39). 
tuberculatus. 
* This species, as observed by Messrs. Sharman and Newton, seems almost 
identical with forms noted as Pleuromya crassa. (See also List of Fossils at end of 
volume.; 
