292 PROCEEDINGS OF THE ACADEMY OF [1888. 



ADDITIONAL OBSERVATIONS UPON THE STRUCTURE AND CLASSI- 

 FICATION OF THE MESOZOIC MAMMALIA. 



J!Y HENRY FAIRFIELD OSBORN. 



In coimectiou -with a visit to the recent Geological Congress in 

 London the writer reviewed the British ]Mnseum collection of Meso- 

 zoic Mammals which formed the principal basis of a recently pub- 

 lished Memoir' and examined also the valuable specimens at Oxford, 

 Bath and York which had previously .been studied merely from 

 the descriptions and figures of Professor Owen and others. Also 

 the NeoplagiauJax specimens in the collection of Dr. Lemoine at 

 Rheims. There are two uudescribed sjoecimens in the Oxford Museum 

 and since the Avriter worked upon the collection in the British 

 Museum, (in- 1886), many of the Purbeck fossils have been much 

 more fully exposed by the further removal of the matrix. Impor- 

 tant features have been brought to light, not visible previously, 

 which lead to a revision of some of the conclusions which were 

 reached upon the evidence then at hand. Greater familiarity with 

 the minute Mesozoic types of molars sharpens the powers of obser- 

 vation and one is more apt to discover new points when on the 

 lookout for them. Thus many inconspicuous but important featui-es 

 were noticed which formerly escaped attention. Some of these, such 

 for example as the identity oi Amhlotherium diViA Stylodon, had been 

 already anticipated, but others, such as the tritubercular molars 

 oi Amjjhdhermm wei'e entirely unexpected. 



The following notes are in abstract from a Postscript to the ^Memoir, 

 which is in preparation, and are not to be considered as final. 



AMPHILESTES, 

 Besides Professor Owen's tyjie, which is preserved in the York 

 Museum,' there are tAVO specimens belonging to this genus at Oxford. 

 In the type, it is somewhat difficult to determine the number of the 

 teeth, as described by Owen, since the incisor and canine alveoli are 

 indistinct, l)ut the Oxford specimens show that there were but six 

 molars instead of seven as conjectured in Lydekker's Catalogue, 

 Part V, p. 271, and adopted by myself, (op. cit., p. 193). In fact, 

 one well preserved specimen, a right ramus seen upon the outer 

 surface, shows but five molars. If this specimen be adult, as seems 

 improbable, it may i*epresent a new genus transitional between 



1 '"'The Structure and Classification of the Mesozoic Mammalia." Journ. of 

 the Acad, of Nat. Sciences of Philadelphia, vol. i.\, no. 2, July 1888. 



'■^ I am indebted to Mr. Plattnauer, the Curator of this Museum, for the oppor- 

 tunilv of freely examininy; this sjiecimen. 



