142 IJULLETIN OF THE 



In both the cat and the f/oj the non-pcrforato space is exceedingly 

 small. In the former it is reduced to a mere elevated rim, and in the 

 latter it is concealed by the anterior edge of the presphenoid. The non- 

 perforate space is well seen in the seal, Phoca vituliua, the opossxim, 

 and the peccari/. In the otter, the hear, and other Carnivora, it is 

 nearly absent, so that the posterior border of the cribriform plate 

 is also the posterior border of the bone. The non-perforate space is 

 in close relation with the orbitosphenoid and the presphenoid, so that 

 the sphenoidal sinuses may be occupied by the lowest of the endo- 

 tnrbinals. 



As is well known, the sphenoidal turbinals in man arc distinct ossi- 

 cles, lying between the etinnoturbinals and the presphenoid. In some 

 mammals, as the sloth, the presphenoid has a group of plates which 

 closely resemble an olfactory plate of the ethmoturbinal, but differing 

 therefrom by the fact that the plates unite with the crest at the basal 

 surface of the cranio-facial axis, instead of being separated by an inter- 

 vening space, as in the ethmoturbinals. A slight tendency in the same 

 dii'cction is seen in the x)eccar>j. Is this group of plates homologous with 

 the sphenoturbinals of man ] 



In the otter {Plate I. fig. 4), the minh, the iveasel, and the hear, the 

 frontal sinuses are occupied by the ectoturbinals. When such frontal 

 development is pi-onounced, the ectoturbinal division of the ethmoid is 

 of a circular form in transverse section and on the encranial surface, 

 while the endoturbinal division is longer than wide. 



The Nasal Surfaces. — Each ethinoturbinal plate is attached to the 

 cribriform plate proximally, to the os planum laterally, and, it may be, 

 to an associate-turbinal distally. Upon the median surfaces the plates 

 remain free, and either end simply, or exhibit a tendency at their ends to 

 form two revolutc parts, the convex surfaces of which api)ear iipon the 

 superficies of the lateral wall of t!ie nasal chamber. In a longitudinal 

 section of the nose the median aspect of the ethmoturbinal is thus 

 made up, in the last-named variety, of the rounded convexities of the 

 plates and the spaces between them. The uppermost of the plates is 

 much longer than the others. . . . The lateral aspect of the nasal cham- 

 ber at the ethmoturbinal region is, therefore, made up simply of those 

 plates which have a conunon plane. The surface gives no impression of 

 the number of the plates present ; for some may not reach the median 

 surface, and from this circumstance be not seen or accounted for. 

 Neither is the suiface a guide ti) tlic length of the plates, since, as the 

 reader has already seen, the cribriform plate is wider above than below. 



