136 BULLETIN OF THE 



The departures from this arrangement in the ethmoid of quadrupeds 

 are so numerous and pronounced that an adherence to a similar plan of 

 description is not satisfactory. 



In proposing modifications, I will use the following language : — 



The ethmoid bone is composed of the ineso-ethmoid and two ethmo- 

 turbinals. The former includes the perpendicular plate and the crista 

 galli ; the latter, as in human anatomy, the lateral masses of the bone. 

 These terms are in general use by English writers. The nasotnrbinal is 

 an ethmoturbinal plate projecting in front of the remaining plates, and 

 forming the superior limit to the series, as seen on the median surface 

 of a longitudinal (sagittal) section. — The "cones of Wistar " form the 

 sphenoturhinals. 



Each ethmoturbinal element is an olfactory plate. The space between 

 any two plates is called an olfactory interspace. 



Each olfactory plate is, as a rule, plicated, and each plication in turn 

 forms an olfactory fold. The free projecting ends of the olfactory plates 

 constitute the olfactory lobes. 



The ethmoturbinal plates are divided into two groups, the ectotur- 

 hinals and the endoturbinals. The ectoturbinal plates are those which lie 

 in a space defined by the frontal bone and the superior maxilla. This 

 space communicates with the nasal chamber at the interspace between 

 the nasoturbinal and the first endoturbinal, as well as by a large oval 

 opening behind the maxillo-turbinal and the vertical plate lying between 

 the superior maxilla and the ethmoid. The ectoturbinal plates are 

 arranged on the lateral sides of the chamber, from which they project 

 inward toward one another, but never to a degree to be seen on the 

 median surface as this is seen in a longitudinal section of the skull. 



The endoturbinal plates are arranged in a series lying beneath as well 

 as medianly to the foregoing. They are placed in oblique parallel rows 

 from above downward, and are best seen in a longitudinal (sagittal) sec- 

 tion of the skull. Each ethmoturbinal plate has a base where it arises 

 from the cribriform plate. The upper border of each plate is its frontal 

 border, while its lower border is its palatal border.* 



The space between the meso-ethmoid and the ethmoturbinal is the 

 septoturbinal space. The lamina uniting the ethmoturbinals one with 



* The temis ecto- and endoturbinal are named with reference to the relations they 

 entertain to the nasal chamber. The ectoturbinals do not appear, with a few excep- 

 tions, on the lateral wall of tlie undissected nasal chamber (see Plate I. fig. 1), while 

 the endoturbinals so appear, or can be made to do so, by producing the axes of the 

 olfactory plates entering into thenr. 



