﻿CHTM^KIDiE. 61 



The posterior outer tritor appears to be much more feebly developed 

 thau in the last-named species, but otherwise the arrangement is 

 similar. Many Kimmeridgian fossils, presumably referable to /. 

 egertoni, exhibit as much antero-posterior elongation as those placed 

 here j and short and long varieties of the mandibular teeth have 

 also been observed in other species, e. g. /. thurmanni (/. brevi- 

 rostris, Newton). 



Form. <Sf Log. Bathonian : Oxfordshire, Gloucestershire, and 

 Normandy. 



P. 3106. Left mandibular tooth, described as the type specimen by 

 Egerton, loc. cit. ; Stonesfield Slate, Stonesfield, Oxford- 

 shire. Enniskillen Coll. 



P. 5150. Imperfect right mandibular tooth, outer aspect; Stones- 

 field. Egerton Coll. 



28592. Nearly similar specimen ; Eyeford, Gloucestershire. 



Purchased, 1853. 



32545. Right mandibular tooth, forming the type specimen of 

 I. tessoni, Agassiz, torn. cit. ; Caen, Normandy. 



Tesson Coll. 



41307. Two imperfect pairs of mandibular teeth ; Caen. 



Purchased, 1869. 



44830. Upper portion of small right mandibular tooth ; Caen. 



Presented by Benjamin Bright, Esq., 1873. 



Ischyodus egertoni (Buckland). 



1835. CMirmra egertonii, W. Buckland, Proc. Geol Soc. vol. ii. p. 206. 



1836. Chimcera egertonii, W. Buckland, Phil. Mag. [3] vol. viii. p. 5. 

 1843. Ischyodus egertoni, Sir P. Egerton, Proc. Geol. Soc. vol. iv. 



p. 156. 

 1843. Chimcsra {Ischyodon) egertoni, L. Agassiz, Poiss. Foss. vol. iii. 



p. 340, pi. xl. c. figs. 1-10. 

 1871. Ischyodus egertoni, J. Phillips, Geol. Oxford, p. 306, pi. xii. 



fig. 24. 



Type. Mandibular tooth, and the theoretically associated palatine 

 and vomerine teeth • Oxford Museum. 



Mandibular tooth with a deeply sinuous oral margin, acute emi- 

 nences corresponding to the beak and outer tritors, and the post- 

 oral margin nearly parallel to the symphysial ; beak-tritor narrow 

 and elongated antero- posteriorly ; outer tritors well developed ; 

 median tritor broad, and occupying the greater portion of the 



