MUSEUM OF COMPARATIVE ZOOLOGY. 145 



sketch the general plan of arrangement of the ethmoid bone in the 

 mammals, and to indicate the relations that the several parts hold one 

 to another. Before describing the bone in the' Cheiroptera, I propose 

 giving detailed accounts of the ethmoid in the cat, the seal, the peccary, 

 the sloth, and the mole ; with the object of bringing together some 

 widely diverse examples, and presenting descriptions which will be suffi- 

 ciently detailed to permit of comparisons being made with those which 

 will follow in the concluding portion of this paper. 



In the home (Plate II. figs. 4, 5) the endoturbinal aspect of the encra- 

 nial surface is concealed from the brain case at its upper third by a trans- 

 verse plate apparently of the frontal bone, but which in reality is an 

 ossification of the ethmoid. The foramina of the endoturbinal surface 

 are arranged elaborately in a crescent extending across the anterior end. 

 The foramina of the ectoturbinal surface are seen in five transverse 

 triangular or clavate clustei's. 



The ethmoid, studied from its lateral aspect, exhibits a treuchant dis- 

 tinction between the endoturbinals and the ectoturbinals by a thin sep- 

 tum extending across the great cranio-facial sinus. Both the turbinal 

 sets lie in this sinus, connected by a thin papyraceous lamina, save at the 

 anterior fourth of the ectoturbinal series, where it is firmly connected 

 by the ends of the olfactory plates to the descending process of the fron- 

 tal bone, as well as with the line of junction this process effects with the 

 orbitosphenoid and the frontal bones. 



Seen in transverse section, the turbinal mass exhibits sharply the di- 

 vision between the two sets of plates. The ectoturbinals are eight in 

 number, including the nasoturbinal. The endoturbinals are five in num- 

 ber, and preserve the order already described as existing in the hog. 

 The last plate sends backward a single folium within the sphenoidal sinus, 

 so that the olfactory apparatus extends a short distance posterior to the 

 encranial surface. 



Seen from the median aspect, the nasoturbinal is seen to assume 

 enormous proportions, being much wider than any of the endoturbinals. 

 Four of the endoturbinals are visible, and all are markedly biconyolute, 

 the convexities of the scrolls alone appearing on the genera] surface. 

 Anteriorly each plate is seen ending simply at the bases, but toward 

 the apices they are more or less lobate. The first ami BOCOnd plates 

 project beyond tin' transverse lamina. 



A small but distinct plate crosses the septoturhinal space obliquely at 

 the orifice of the sphenoid sinus. The septum is distinctly foliated 

 opposite the third, fourth, and fifth plates. 



vol.. v. no. 3. in 



