684 M. L. DOLLO. 



skulls of apes in the Royal Belgian Museum of Natural History, 

 and that he will shortly publish an account of them. 



To sum up, M. Albrecht's arguments lead, on the whole, to 

 the following two conclusions : 



1st. The quadrate cannot form part of the interfenestral 

 chain of bones of Mammalia. 



2nd. One of the two bones (the zygomatic portion) formed 

 by the division of the so-called squamosal is doubtless the 

 homologue of the quadrate of Sauropsida. 



I shall examine these two statements successively, in order 

 to show whether the results of my own observations tend to 

 confirm or invalidate M. Albrecht's conclusions. 



I. 



Can the quadrate form a part of the interfenestral chain ? 



It is evident that if there were found simultaneously existing 

 in the same animal a mandible composed of six normal elements, 

 a true quadrate, and a malleus, it would immediately follow 

 that it was impossible that that quadrate could form any part 

 of the chain of ossicula auditus, for — 



1st. It could not be confounded with the malleus, because 

 there would already be one there. 



3nd. It would be still more impossible to identify it with 

 the remainder of the interfenestral chain, because it would be 

 situated outside the malleus, and would not touch any of the 

 remaining ossicula. 



Everything depends, therefore, on the discovery of a malleus 

 in the condition described above. Now, I have found in several 

 Lacertilia (Leiolepis guttatus, Ctenosaura pectinata, 

 Uromastix spinipes, Lophyrus dilophus, Basiliscus 

 vittatus) a small bone which appears to answer the question. 

 I shall endeavour to prove that it has really the morphological 

 value of a malleus. 



a. Fn-stly, it has the form of a malleus ; it being possible to 

 distinsuish in it : 



