MUSi:U.M OF COMPAUATIVE ZOOLOGY. 145 



sketch tlio general })laii of arnuigeinent of the ethmoid bono hi the 

 mammaLs, and to indicate the rehitions that tlie several parts hold one 

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

 giving detailed acconnts 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 ])resenting descri2:)tions wdiich will be snffi- 

 ciently detailed to permit of comparisons being made with those which 

 will follow in the concluding jjortion of this paper. 



In the horse (Plate II. figs. 4, 5) the endotnrbinal aspect of the encra- 

 nial surface is concealed from the brain case at its i;pper 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 e.\teuding across the anterior end. 

 The foramina of the ectoturbinal surface are seen in five transverse 

 triangular or clavate clusters. 



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

 tinction between the cndoturbinals 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 ])latcs to the descending process of the fron- 

 tal bone, as well as with the line of junction this process eiiects w'itli the 

 orbitosphenoid and the frontal bones. 



Seen in transverse section, the tiu'binal mass exhibits sharply the di- 

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

 numl)er, including the nasoturbinal. The cndoturbinals are five in nuni- 

 l)cr, and preserve the order already described as existing in the hog. 

 The last jjlate 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 cndoturbinals. 

 Four of the cndoturbinals arc visil>le, and all are mai'kedlv bic'onvolutc, 

 tiic convexities of the scrolls alone a])pearing on the general surface. 

 Anteriorly each plate is seen ending sinqdy at the bases, lint toward 

 tiie apices they are more or less lobate. The first and second jilates 

 ])roject beyond the transverse lamina. 



A small but distinct plate crosses the scptoturbin;d space obliquely at 

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

 oi)positc the third, fourth, and fifth ))lates. 



vol.. X. — Ml. :;. 10 



