1254 General Notes. [ December, 
extremity is the stapes proper. The oblique perforation of its 
base is a character which has not been hitherto observed in any 
reptile, not even in the allied form Hatteria (Huxley). If, as is 
probable, the perforation is homologous with the foramen of the 
mammalian stapes, we have here another point of resemblance to 
this class. The longer proximal branch of the columella has only 
halt the width of the stapedial portion, and its long axis makes 
an obtuse angle with that of the latter. It is perhaps the ossified 
suprastapedial cartilage of Huxley, which that author states (An- 
atomy of Vertebrated Animals, p. 77) is not ossified in any of the 
living Sauropsida. Huxley supposes this cartilage to be the homo- 
logue of the incus, and remarks’ that in a young Mammalian fæ- 
tus “it appears exactly as if the incus were the proximal end of 
the cartilage of the first visceral arch.” This identification will 
require an excessive abbreviation of the stapes in Clepsydrops, and 
until this is proven I prefer to call this process the epicolumella 
(see Pl. xxxviii, fig. 2).. The columella now described, resembles 
a rib, of which the epicolumella resembles the head, and the stapes 
the tubercle. If this process be the incus, the stapes is shortened 
as in the majority of Mammalia, unless the primitive suture be- 
tween the two be longitudinal. The form and position of the true 
stapes give support to the view of Salensky, that it is not part ot 
a true visceral arch, but is developed in the connective tissue 
„surrounding the mandibular artery. We see that in this i 
saurian 1t is not the proximal part of the arch, and surrounds t! 
mandibular artery. The columella is d 
tinct elements. This is clearly indicated by its abru 
distally by a rough sutural surface. h gg 
distad to the stapes, it is homologous with the cartilage, whic æ 
been shown by Peters? to be distinct in Hatteria, crocodi p ey 
bones are homologous with the ossicula auditus, 1s incorrect. ae 
Pelycosauria will probably come under the head of Saur ae 
malleoferes” of Albrecht. We have here an approxima ing 
the Mammalia in two points: (1) The perforation and ? rast’ 3) is i 
of the stapes; (2) and the ossification of the incus, which u 
distinct from the malleus, thus furnishing homologues of however, 
cipal ossicles of the ear. It is unnecessary to observe, 90% 
that this part of the skeleton does not resemble the corres 
part in the known Monotremes. 
EXPLANATION OF PLATE XXXVI. ie plate.) _ 
(I am indebted to the American Philosophical Society for the use o antl d 
Fic 1.—Clepsydrops leptocephalus Cope, right quadrate bone (Q) yooh bone ® 
zygomatic process (z) from the right, or external side. Zh PINE 
- 
1p lings Zool. Society, London, 1869, p. 391- 
2 Monatsberichte der Academie Sciences, Berlin, 1868 (p- 592) 187° 
