410 Mr. R. Broom on the 



logical value of the malleus and incus. The researches of 

 Peters *, Dollo f, Baiir|, and Gadow § place it beyond doubt 

 that the ]\Iammalian auditory ossicles are together homolo- 

 gous with the Reptilian columella auris and extra-columella, 

 and that the malleus and incus can never have taken any part 

 in the articulation of the jaw. 



An entirely different view of the fate of the quadrate has 

 recently been revived by Albrecht ||, and has been supported 

 by Dollo, Copell, and Baur. According to this view the 

 quadrate is represented by the zygomatic portion of the 

 squamosal. It is highly probable that the Mammalian 

 squamosal represents more than one element ; but the palteon- 

 tological evidence which would find in it the quadrate is 

 unsatisfactory, the zygomatic portion being most probably 

 homologous with the quadrato-jugal. 



Gadow and Seeley ** advocate the view of Cuvier and 

 Owen, that the quadrate is represented by the tympanic bone. 

 Thisj however, involves a gradual shifting back of the quad- 

 rate from the articulation, which, though conceivable, is not 

 borne out by positive evidence eitlier from palaeontology, 

 embryology, or comparative anatomy. 



The Mammalia and Rcjjtilia seem to have had a common 

 origin in a group of highly developed Amphibians, of which 

 no remains have as yet come to light, but of which Pareia- 

 sauriis is the nearest ally as yet known. In these ancestral 

 forms there was in all probability but a feebly developed 

 flattened quadrate, probably ossified and articulating with the 

 quadrato-jugal, squamosal, and pterygoid. In Pareiasaiirus 

 kSeeleytt says the quadrate bone "would appear to have been 



* W. Peters, " Uebf>r die Gehorlmockelclien und ihre Verliiiltniss zu 

 don ersten Zungeiibogen boi Sphcnodon jnindatus," Moiiatsber. d. k. 

 preuss. Akad. d. Wiss., Berlin, 1874. 



t L. Dollo, "On the Malleus of the Lacertilia, &c.,'' Quart. Joiiru. 

 Micr. Sc. 188;i. 



X G. Bniir, " On the Quadrate in the j\lamnialia," Quart. Jouru. Micr. 

 Sc. 18e7. 



§ IL CTadow, "On the Moditications of the First and Second Visceral 

 Arches, iS:c.," Thil. Trans, vol. clxxi.v , 1888. 



II P. Albrecht, ' Sur la valeur uiorphologique de rarticulation mandi- 

 bulaire, &c.,' ]?ruxelles, 1883. 



^ E. D. Cope, ''The Kelations between the Theroniorphous Peptiles 

 and the Monotreme Mammalia,"' Vnc. Anier. Assoc. Adv. Soi. vol. xxxiii. 

 1884. 



** H. G. Seelev, "On the Anomodont Ileptiliaand their Allies," Phil. 

 Trans, vol. clxxx.,* 1889. 



tt II. O. Seeley, " On P«rem.«fl»/r//.v /;(>«/>/V/<7K< (Owen), and the Signifi- 

 cance ot its Atiinitirs to Aniphibiinis, Kepliles. and Mauinials.' Phil. 

 Trans, vol. clxxix.. 1888. 



