24- WILLIAM K. GREGORY 
of the primary lower jaw; the developing incus has every appear- 
ance of representing the quadrate and has similar relations with 
reference to the stapes (p. 28), to the chorda tympani nerve 
(fig. 21), to the squamosal (p. 26), to the inner ear (p. 27) 
and to the tympanic cavity (p. 25). 
To this remarkable series of parallel relations in mammals 
and reptiles, Gaupp has recently made known an important 
addition. 'The malleus of mammals is a composite structure 
consisting first of a portion preformed in cartilage (comprising 
the main mass of the bone and the handle, or manubrium) and 
secondly of a membranous portion forming the anterior process 
proc.an t 
(Goniale) 
proc brev. 
/ 
MAAN 
ji AN 
Fig. 17 Developing lower jaw and auditory ossicles of Tatusia hybrida. 
(Based on Parker, 1885, pl. 5, fig. 3 and pl. 6, fig. 3a.) 
The malleus (M1.) isseen to form the articular region of the Meckelian cartilage (Mck.); the dermal bone 
ensheathing it below, forming the anterior process of the malleus, is homologized by Gaupp with the rep- 
tilian goniale. The handle of the malleus (man. mal.) is inserted in the tympanic membrane which is 
stretched on the tympanic annulus (Ty.). 
(processus anterior s. Folianus, fig. 17). The cartilaginous por- 
tion of the sig ire! ee long been regarded as the articular of 
reptiles; the dermal portion is therefore regarded by Gaupp as 
the goniale or prearticular which in the reptiles forms the medial 
internal extension of the articular. Moreover, both the goniale 
of reptiles and the anterior process of the malleus of mammals 
are sometimes pierced by the chorda tympani nerve. For these 
reasons Gaupp regards the malleus of mammals as the homo- 
logue of the gonio-articulare of reptiles. 
The evidence favorable to, or consistent with, Reichert’s theory 
offered by the Theriodont reptiles, has until recently remained 
