410 
Mr. R. Broom on the 
logical value of the malleus and incus. The researches of 
Peters * * * § , DolJo f, Baur and Gadow § place it beyond doubt 
that the Mammalian 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, Cope^I, 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 palaeon- 
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. 
This, however, involves a gradual shifting back of the quad- 
rate from the articulation, wdiich, though conceivable, is not 
borne out by positive evidence either from palaeontology, 
embryology, or comparative anatomy. 
The Mammalia and Reptilia 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- 
saurns 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 Pareiasaurus 
Seeley jf says the quadrate bone u would appear to have been 
* W. Peters, u Ueb^r die Gehorknockelchen und ihre Verhaltniss zu 
den ersten Zungenbogen bei Sphenodon punctatuSj ' Monatsber. d. k. 
preuss. Akad. d. Wiss., Berlin, 1874. 
t L. Dollo, “ On the Malleus of the Lacertilia, &c.,” Quart. Journ. 
Micr. Sc. 1883. 
f G. Baur, 61 On the Quadrate in the Mammalia/’ Quart. Journ. Micr. 
Sc. 1887. 
§ H. Gadow, “On the Modifications of the First and Second Visceral 
Arches, &c.,” Phil. Trans, vol. clxxix , 1888. 
|| P. Albrecht, ‘ Sur la valeur morphologique de l’articulation mandi- 
bulaire, &c.,’ Bruxelles, 1883. 
IT E. D. Cope, “ The Relations between the Theromorphous Reptiles 
and the Monotreme Mammalia,” Free. Amer. Assoc. Adv. Sci. vol. xxxiii. 
1884. 
** H. G. Seeley, “On the Anomodont Reptilia and their Allies,” Phil. 
Trans, vol. clxxx., 1889. 
tt H. G. Seeley, “On Pareictsaurus bombidens (Owen), and the Signifi- 
cance of its Affinities to Amphibians, Reptiles, and Mammals,” Phil, 
Trans, vol. clxxix., 1888. 
