MUSEUM OV COMPAliATIVE ZOOLOGY. 143 



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

 necessity longer tliau 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 dor/ (Plate 1. fig. 1), for 

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

 placed from above downward, and witiiin outward. Two conspicuous 

 convolutions ai'c present at the distal end, tlie lower one of which alone 

 lies toward, but not on, the median surface. The second plate ])os- 

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

 fourth are very short, biconvolute, and directed uj)ward and forward. 

 None of the ectoturbinals ap[iear on the longitudinal surface of tlie 

 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 pai'ts are slun-t 

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

 of the plate, — one on tlie 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, liut they are less conspicuous. The third and remaining 

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

 mun, 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 ])latc or 

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

 non-convolute structure, intermediate l)etweon the two sets of plates. 



The endoturbinals are always arranged in tiers one above another. 

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

 second of the })lates descends, and may follow the curve of the sides and 

 the bottom of the nasal cliamher as far as the meso-cthmoid, along 

 which it ascends a short distance. The plates in this portion of the cth- 

 motui'binal in the dog ai'e from three to four in nunil)er. The olfactory 

 plates tend to unite anterioi'ly. Thus two to three plates luiite to form 

 the nasoturbinal in the dor/. The lower endoturl)inal jdates unite in 

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

 ti'ansversG lamina of Sli-auss-Diirckheim. It is constantly present, 

 stretching across tlse septoturbinal space to the vomer, against -which 

 it rests. 



Tlie cctoturbiurd ]ilates may bo rudimentary or "• absent. They would 



