MUSEUM OF COMPAEATIVE ZOOLOGY. 143 



so that a plate extending from the last-named to the median surface is of 

 necessity longer than one extending between similar points below. 



In the transverse section it will be seen that a number of the plates 

 have failed to reach the median surface. In the dog (Plate I. fig. 1), for 

 example, the ectoturbinals are four in number. The first is obliquely 

 placed from above downward, and within outward. Two conspicuous 

 convolutions are present at the distal end, the lower one of which alone 

 lies toward, but not on, the median surface. The second plate pos- 

 sesses a single convolution, which is directed outward. The third and 

 fourth are very short, biconvolute, and directed upward and forward. 

 None of the ectoturbinals appear on the longitudinal surface of the 

 nasal chamber. The first endoturbinal is long and complex. It is di- 

 rected forward and upward, and nearly touches the median convolution 

 of the first ectoturbinal. It is biconvolute, but the parts are short 

 and not incurved. Three secondary convolutions are seen on the sides 

 of the plate, — one on the upper, and two on the lower aspect. Both of 

 the latter reach the surface of the longitudinal section. The second 

 endoturbinal is the longest of the series, and touches the septum. A 

 single primary convolution is directed upward, and much convoluted. 

 A single upper and two lower secondary convolutions are seen, as in the 

 first plate, but they are less conspicuous. The third and remaining 

 plate is the smallest of the endoturbinals, and arises from the os pla- 

 num, as this structure is seen in the section. It is directed upward and 

 inward, to appear on the longitudinal section. It presents a single con- 

 volution. Immediately beneath the last plate, the transverse plate or 

 lamina is seen. The nasoturbinal is seen in the section as a minute 

 non-convolute structure, intermediate between the two sets of platea 



The endoturbinals are always arranged in tiers one above another. 

 All originate from the lateral surface. In the dog (Plate I. fig. 2) the 

 second of the plates descends, and may follow the curve of the sides and 

 the bottom of the nasal chamber as far as the meso-etlnnoid. along 

 which it ascends a short distance. The platea in this portion of the eth- 

 moturbinal in the dog are from three to four in number. The olfactory 

 plates tend to unite anteriorly. Thus two to three plates unite to form 

 the nasoturbinal in the dog. The lower endoturbinal platea unite in 

 front by broad, thin plates. These, taken collectively, constitute the 

 transverse lamina of Strauss-Durckheim. It is constantly present. 

 stretching across the septoturbinal space to the vomer, against which 

 it. rests. 



The ectoturbinal plates may be rudimentary or absent. They would 



