110 
SELACHII. 
Type. Upper dental plates; British. Museum. 
Teeth very massive, the coronal contour transversely arched, 
especially in the upper jaw. Longitudinal superficial strise well 
marked in unabraded specimens. Median teeth in the adult rarely 
or never more than five times as broad as long; lateral teeth much 
longer than broad. 
The specimens figured respectively under the names of M. con¬ 
tractus, JSl. stricitus, and J\I. toliapicus, by Dixon andGeinitz, toe. cit., 
are examples of the lower dentition of M. clixoni : so also probably 
is the type specimen of M. heteropleurus , Agassiz. Numerous 
measurements of the teeth at various stages of growth are given 
by the present writer, loc. cit. 
Form. 4' Loc. Barton Clay (Upper Eocene) : Hampshire. Braek- 
leskam Beds (Middle Eocene): Sussex. Phosphate Beds (Middle or 
Upper Eocene) : Helmstedt, near Harzburg, Brunswick. (?) Lower 
Eocene : Cuise-la-Motte, Oise, Erance. 
' Upper Dentition. —Bracklesham Beds, Bracklesham Bay. 
25814, 25621, 25623, P. 434. Type specimens figured by Dixon, 
op. cit., and noticed by the present writer, loc. cit. p. 41. 
Dixon Coll., and (P. 434) Purchased, 1882. 
25844. Abnormal specimen, having the lateral plates in the form of 
irregular parallelograms, referred to by Dixon, op. cit. 
p. 198 . Dixon Coll. 
25845-6, 25648-9, 25654. Plates in connected series. Dixon Coll. 
25864. A very fine connected series of nine median teeth, with two 
lateral rows on each side ; the unworn surface is somewhat 
longitudinally striated and wrinkled. Dixon Coll. 
38839, 38841-46. Plates in connected series. The first specimen 
is noticed by the present writer, loc. cit. p. 41. 
BoiverbanJc Coll. 
P.435, P. 437. Six examples. Purchased, 1882. 
P. 5384. Four medium-sized specimens. 
Presented by P. E. Coornbe, Esq., 1888. 
P. 1496, P. 1498, P. 1498 a, P. 1504 a, P. 1507 c, P. 1509. Twenty 
examples. No. P. 1498 a is noticed by the present writer, 
loc. cit. p. 41. Egerton Coll. 
P. 3044, P. 3044 a-c. Twelve examples. Nos. P. 3044 a, b, are 
noticed by the present writer, loc. cit. p. 41. 
Enniskillen Coll. 
