450 Edward Phelps AUis jr., 



not included in that primary involution that gave rise to the vesicle 

 of the inner ear. The extrascapular bone, already naturally perforated 

 near its centre, would foretell, for it would hardly seem possible that 

 it could represent, the annulus tympanicum. 



Further reference should here be made to the Nasenmuschel of 

 Erdl's descriptions. This bone is said by Erdl to form an anterior 

 continuation of the chain of orbital bones, and is said to be perforated 

 by a foramen for the passage of the olfactory nerve. This led me 

 to suggest, in an earlier work [3, p. 454], that this bone might be 

 the homologue of the posterior process of the premaxillary of Amia, 

 and that it, and also the process in Amia, were perhaps sensory 

 ossicles developed in relation to the nasal sac. My present work 

 shows that this opinion, whether a proper one or not, was not based 

 on fact. The Nasenmuschel, as already stated, lodges, in a groove on 

 its lateral edge, the anterior section of the main infraorbital canal. 

 This part of the bone is thickened, as is also the anterior edge of 

 the bone, anterior to the anterior end of the sensory groove. The 

 remainder, or body of the bone is simply an exceedingly delicate 

 plate that is continuous with the deeper layers of this thickened 

 anterior, or antero-lateral edge of the bone; the thickened edge of the 

 bone thus rising above the body of the bone. The entire bone is 

 oval in general shape, is convex internally, and concave externally; 

 and it immediately underlies and hence lodges, and protects from be- 

 neath, the nasal sac. The sensory epithelium of the sac lies mainlj'^ 

 in the anterior third or half of the bone, and the olfactory nerve 

 reaches it by passing over, that is superficial to, the mesial edge of 

 the bone, its place of passage being marked by a slight and evenly 

 rounded incision. The nerve does not traverse the bone, as Erdl states, 

 and the body of the bone is not even perforated by a foramen such 

 as Erdl shows. The olfactory nerve, as it passes over the edge of 

 the bone is enclosed in tough fibrous tissue that is closely attached 

 to the edge of the bone, and this tissue may, perhaps, ossify in older 

 specimens, thus in that case giving rise to the condition described 

 by Erdl. Whether there are here two bones, of different origin, fused, 

 or not, I can not decide. If there be, the bone that lodges the nasal 



