jfo. 3. — On a Revision of the Uthmoid Bone in the Mammalia, ivith 

 special Reference to the Description of this Bone and of the Sense of 

 Smelling in the Cheiroptera. By Hahrison Allen, M. D., Profes- 

 sor of Physiology in the University of Pennsylvania. 



In the Bulletin of the Museum of Comparative Zoology dated Febru- 

 ary, 1880, I described briefly some peculiarities of structure I had de- 

 tected in the ethmoid bone of the Cheiroptera.* It is my purpose in 

 this communication to extend my remarks in the same direction, and by 

 way of introduction to give a brief account of the ethmoid bone as it is 

 met with in the mammals generally. 



The ethmoid bone in mammals lies within the ethmoidal notch of the 

 frontal bone, and is in all but a few groups (e. g. in Primates, Quadru- 

 mana, and some of the genera of Felidae) protected laterally by the 

 descending process of the frontal bone, the orbital process of the palatal 

 bone, and the orbital process of the orbito-sphenoid bone. In the nasal 

 chamber it is protected above by the nasal bone and in part by the 

 vomer. Its several portions lie in the nasal chamber and in the frontal 

 and sphenoidal sinuses. With a near approach to accuracy, it may be 

 said that the ethmoid is included between the following openings : the 

 optic, the ethmoidal and the sphenoidal foramina, and the lachrymal 

 and the infra-orbital canals. The suture between the palatal bone and 

 the superior maxilla in the roof of the mouth corresponds nearly to the 

 anterior limit of the cthmoturbinals. 



The Nomenclature of the Subdivisions of the Ethmoid Bone. — The 

 ethmoid bone of the human subject is described by anatomical writers as 

 composed of a pair of lateral masses, sponges, or labyrinths, united to a 

 perpendicular plate by means of the cribriform plate, the projection of 

 the former above the latter constituting the crista -galli. Each lateral 

 mass in turn is composed of ethmoid cells, and presents upon its median 

 surface two scrolls. The " cones of Wistar " are a pair of symmetrical 

 ossicles appended to the lateral masses posteriorly, and are not of olfac- 

 tory significance. 



* The prodrome of this memoir, as aniioiuiceJ in the above-named paper, has not 

 been followed in all respects. The points of difference, however, do not demand 

 special attention. 



VOL. X. NO. 3. 



