On some Teeth of new Chimccroid Fishes. 13 



III. — On some Teeth of neio Chimceroid Fishes from the 

 Oxford and Kimmeridge Clays of England. By A. Smith 

 Woodward, F.L.S., F.Z.S., of the British Museum 



(Natural History). 



[Plate III.] 



Notwithstanding the fact that the number of forms of 

 Chimceroid teeth known from Mesozoic formations is ah-eady 

 large, there are still several specimens in the British Museum 

 that cannot be assigned to the genera and species as yet 

 described. More especially does this remark apply to the 

 collection of Alfred N. Leeds, Esq., of Eyebury, lately 

 received ; for if the characters of tlie teeth can be relied upon 

 in generic diagnoses (as seems probable), the small series 

 of specimens from the Oxford Clay of Peterborough, collected 

 by Mr. Leeds, makes known the occurrence of two distinct 

 genera hitherto unrecognized. There are also some small 

 teeth from the Kimmeridge Clay of Weymouth, which are 

 partly identical with one of Mr. Leeds's fossils, and partly 

 seem to indicate even a third genus as yet unknown in the 

 Jurassic. It is with the systematic arrangement of these 

 specimens that the present communication deals. 



A general summary of existing knowledge on the subject 

 of the Mesozoic Chimceroid fishes will be found in the second 

 part of the British Museum * Catalogue of Fossil Fishes,' and 

 the following descriptions are arranged to be uniform in style 

 with that work. 



Genus Pachymylus, nov. 



Diagnosis. — Mandibular tooth massive, with a well-defined 

 hard layer upon the outer aspect immediately below the oral 

 margin, and a very broad symphysial facette; one median 

 tritor forming a prominent boss ; anterior and anterior-outer 

 tritor absent ; posterior outer tritor repre'sented by few small 

 patches. Palatine tooth robust, with a single, large, promi- 

 nent tritor. 



Bemarhs. — The upper and lower teeth, here placed together, 

 have not yet been found in natural association ; but they 

 agree so closely in character that there can be no doubt as to 

 their pertaining to one and the same fish. Regarded as 

 Jurassic fossils they are of much interest, from the great 



