8 FOSSIL REPTILIA OF THE 
but the quarrymen extracted the hind part of the cranium (PI. III, fig. 1). It shows 
a hemispheroid condyle (1) 2 inches 8 lines in basal diameter. The foramen magnum 
is a full transverse ellipse, 1 inch 3 lines across. The broad and low occipital surface 
includes the thick horizontal backwardly projecting paroccipital ridges, below which 
extend still more backward and somewhat downward the short and broad tympanics, 
terminated each by a condyle convex in its outer two thirds, concave transversely at the 
inner third: the breadth of this condyle (gs) is 5 inches. 
The upper transverse ridge of the occiput is broken away. The parietal region (7) is 
formed by a lofty median vertical wall of bone, slightly expanding below to form the side 
walls of a miserably small cerebral cavity. 
[have neither respect nor inclination for undue multiplication of genera ; but the degree 
of difference in the number of mandibular teeth and extent of the symphysis tempts to a 
view of the present evidence of Pliosaurus trochanterius as testifying to something more than 
specific distinction from the Pliosaurus grandis. I leave, however, the opening for 
a “name” to any labourer in gattungsmackery who may yield to the temptation. 
The Plhosaurus grandis retains more similarity with the type Sauropterygians (P27. 
dolichodeirus, e. g.) in the proportions of the symphysis and of the number of symphysially 
located teeth. Nevertheless, modifications in these particulars are presented, though in 
a minor degree, by species of true Plesiosauri (compare, in the ‘Monograph of the 
Fossil Reptilia of the Liassic Formations,’* Pl. III, fig. 2 (Plesiosaurus dolichoderius), 
with Pl. XVI, fig. 2 (Plesiosaurus Hawkinsit)). 
The specimen figured in Pl. III, fig. 2, includes the part of the maxillary bones, 
with eight or nine pairs of alveoli at or very near to the hind end of the series, of a 
smaller individual of the Phosaurus trochanterius than that to which the lower jaw, figs. 
3, 4, 5, belongs. The transverse section above the figure shows the medial (20) and inner 
alveolar (21) palatal ridges ; also the prominent longitudinal medial ridge on the upper 
surface (here turned down) of that part of the skull; a similar rismg occurs in Plesio- 
saurus (comp. Monogr. cited,* Pl. III, fig. 1, Ples. dolichodeirus, Pl. VI, Ples. homato- 
spandylus, Pl. XVI, fig. 1, Ples. Hawkinsii). 
This fragment measures 11 inches in length, and 6 inches in greatest breadth. It is 
from, the same locality and formation as the larger skull, viz., the Kimmeridge Clay of 
Kimmeridge. Both specimens have been liberally presented to the British Museum by 
the discoverer, J. C. Mansei, Hsq., F'.G.S. 
PLIOSAURUS PORTLANDICUS, Owen. Plate IV, figs. 1, 2, 3. 
The true and sufficient generic distinction from Plesiosaurus indicated by the term 
Pliosaurus, and suggested by modifications of the shape of the teeth and proportions of 
* Vol. of Pal. Soc. for the year 1863, published 1865. 
