﻿UIllSLaSlUDJE. B7 



Type. Skeleton ; Paheontological Museum, Muuich. 



A species known only by a small skeleton, which exhibits the 

 outer lateral aspect of the dentition. Head occupying somewhat 

 less than one-quarter of the total length ; tail rapidly tapering. 

 Space between pectoral and pelvic fins about equal to the distance of 

 the former from the end of the snout. Dorsal fin-spine compara- 

 tively short and robust, its length about equal to the depth of the 

 trunk at its point of insertion. Oral margin of mandibular tooth 

 regularly and deeply sinuous ; post-oral margin nearly parallel with 

 the symphysial margin. 



Form. $• Loc. Lower Kimmeridgian (Lithographic Stone) : 

 Bavaria. 



Not represented in the Collection. 



Ischyodus planus, Newton. 



1878. Ischyodus planus, E. T. Newton, Chirnseroid Fishes Brit. Cret. 

 Rocks (Mem. Geol. Surv.), p. 37, pi. xii. figs. 1, 2. 



Type. Mandibular tooth ; collection of Thomas Jesson, Esq. 



A species of large size, known only by the mandibular teeth. 

 Mandibular tooth with a gently wavy oral margin (and beak pro- 

 bably short) ; beak-tritor single, laminated ; outer tritors rudimen- 

 tary ; median tritor large, occupying nearly half of the oral surface, 

 and posteriorly situated. 



Form. Sf Loc. Cambridge Greensand : Cambridge. (?) Upper 

 Chalk: Norfolk. 



48945. Fragment of mandibular tooth, doubtfully assigned to this 

 species by Newton, op. cit. p. 38 ; U. Chalk, Norwich. 



Bayfield Coll. 



Ischyodus thurmanni, Pictet & Campiche. 



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



p. 156 (name only). 

 1843. Chimcera (Ischyodon) brevirostris, L. Agassiz, Poiss. Foss. vol. hi. 



p. 344 (name only). 

 1843. Chimcera (Ischyodon) agassizii, L. Agassiz (errore), ibid. pi. xl. c. 



figs. 14, 15. 

 1858. Ischyodon thurmanni, Pictet & Campiche, Foss. Terr. Cretace 



St.-Croix (Pal. Suisse), p. 76, pi. ix. fig. 8. 

 1862. Ischyodus agassizii, W. H. Bensted (errore), Geologist, vol. v. 



p. 378. 

 1867. Ischyodus bouchardi, H. E. Sauvage, Catal. Poiss. Second. Bou- 



lomiais (Mem. Soc. Acad. Boulogne-sur-Mer. vol. ii.), p. 81, pi. iv. 



fig. 6. [Mandibular tooth.] 



f2 



