32 
Ichthyosauria. 
Wall-case, 
No. 14. 
Table-cases, 
Nos. 13 and 
14. 
Fig. 40, A). They are primarily divisible into a precaudal 
and a caudal series without any differentiated sacrum, the pre- 
Fio. 33.— Left lateral aspect of the skull of Ichthyosaurus communis (Conybeare) ; from 
the Lower Lias, Lyme liegis, Dorset (about ^ nat. size). The body was entirely devoid 
of any hard exo-skeleton. 
Fig. 39. — Left lateral and anterior aspects of the centrum of an early posterior dorsal 
vertebra of Ichthyosaurus trigonus (Owen); Kimmeridge Clay, Stanton, a, upper, 
b, lower costal tubercle. 
ARC 
Fig. 40. — Tbe centrum of an anterior dorsal vertebra of Ichthyosaurus entheciodon (Hulke), 
Kimmeridge Clay, Wilts, a, section: b, anterior aspect; c, left lateral aspect. 
caudal s have an upper and a lower costal or rib-tubercle on 
the centrum ; the caudals have a single tubercle ; the neural 
arches are attached by synchondrosis (by cartilage or gristle) to 
