LABKID.I:. 
551 
Egertonia isodonta, Cocchi. 
18G6. Etjertonia isodonta, I. Cocchi, foe. cit. p. 122, pi. iv. figs. 1, 2. 
Type. Convex (upper) pharyngeal dentition ; British Museum, 
type species, with all pharyngeal teeth hemispherical, and 
the dental plate measuring as much as O' 025 antero-posteriorly. 
Form., tj- Loc . Lower Eocene (London Clay) : London Basin. 
38814. Type specimen, figured he. cit. pi. iv. fig. 2 ; Sheppey. 
Bowerbanlc Coll. 
587. Concave (lower) pharyngeal dental plate, described and 
figured loc. cit. p. 123, pL iv. fig. 1 ; Sheppey. 
Egerton Coll. 
28713 a. More imperfect specimen ; Sheppey. Purchased, 1853. 
Ihe following species has also been described, but is not repre- 
sented in the Collection : — 
Egertonia gosseleii, C. H. Leriche, Ann. Soc. Geol. Nord, vol. xxix. 
(1901), p. 175, pi. i. fig. 1.— Lower Eocene ; Cuis, Epernay, 
Marne. [Upper pharyngeal dentition ; University of 
Lille.] 
Genus PLATYL-ffiMUS, Dixon. 
[Geol. Sussex, 1850, p. 205.] 
An extinct genus, known only by the pharyngeals, each nearly 
or completely covered by a crushing plate, which consists of coarse 
'•ascular dentine invested with a very thin layer of ganodentiue. 
L pper pharyngeal bones separate. 
Platylaenaus colei, Dixon. 
1850. PUitylannus colei, F. Dixon, Geol. Sussex, p. 205, pi. xii. figs. 
11-13, pi. x. fig. 23. 
Type. Lower pharyngeal ; British Museum. 
The type species, with triangular lower pharyngeal somewhat 
more than two thirds as long as broad. Upper pharyngeal dental 
plate slightly concave. 
Form. Loc. Middle Eocene : Sussex. 
25692. Lower pharyngeal dental plate, figured by Dixon, op. cit. 
pi. xii. fig. 12, to be regarded as the type specimen ; 
Braeklesham Beds, Brackleshara, Sussex. Dixon Coll. 
