40 
ACTINOPTEETGIT. 
Pachyrhizodus gardneri (Masou). 
1837-44. Hypsodon leicesiensis, L. Agassiz, Poiss. Foss., Feuill. p. 104 , 
vol. V. pt. i. p, 99, pi. xxY a. figs. 2, 4, pi. xxv b. figs. 6, 7 (in part). 
1846. “ Reptile or Fish,” T. Smith, Loud. Geol. Journ. p. 21, & woodc, 
1869. Acrodontosaurus gardneri, J. W. Mason, Quart. Journ. Geol. 
Soc. vol. xxv. p. 444, pi. xix. 
1877. Hypsodon leioesiensis, E. T. Newton, Quart. Journ. Geol. Soc. 
vol. xxxiii. p. 508, 
1888. FacliyrMzodus gardneri, A. S. Woodward', Proc. Geol. Assoc, 
vol. X. p. 314. 
Type. Portion of mandibular ramus ; British Museum. 
A large species, the mandible attaining a length of at least 0*3. 
Dentigerous portion of premaxilla nearly half as broad as long, its 
marginal teeth not inclined outwards, its inner teeth with much- 
expanded base, very stout and curved inwards. Dentary bone very 
deep, but rapidly contracting in front into a narrow thickened 
symphysis, and sharply bent inwards in the lower two-thirds 
throughout its length; its maximum depth equal to the base-line 
of 6 anterior teeth ; a small groove on the outer face extending 
from the middle of the symphysial border in a longitudinal direc¬ 
tion and slightly upwards until lost at the oral border; the stout 
incurved teeth somewhat over 20 in number if all were present. 
Form. 4" Toe. Turonian : Kent and Sussex. 
4105. Fragmentary remains of jaws in a block of chalk, partly 
noticed and figured by Agassiz, tom. cit. p. 99, pi. xxvu. 
figs. 2, 4, among the type specimens of Hypsodon leivesien- 
sis; Chalk, Lewes. There are portions of the dentar}’- 
of both sides, that of the left only shown in the figure. 
The characteristic premaxilla of the left side, much 
fractured, is exposed from the oral aspect and displays 
the two large inner teeth besides two of the marginal 
teeth. Remains of the left maxilla exhibit a series of 
smaller teeth, Mantell Coll. 
41674. Slab of chalk with scattered remains of head, noticed by 
Toulmin Smith, loc. cit. 1846; Lower Chalk, Kent. 
Among the fragments of jaws the most conspicuous is the 
imperfect right dentary, exposed from within and partly 
shown in Smith’s upper figure, loc. cit. The teeth on this 
bone are large and smooth, curved inwards, and arranged 
ill very close series, the base of each much thicker 
measured from its outer to its inner face than from side 
to side ; the alveolar border is greatly thickened to support 
