MUSEUM OF COMPARATIVE ZOOLOGY. 143 



SO that a plate extending from the last-named to the median surflice is of 

 necessity longer than one extending between similar points below. 



Ill the transverse section it will l)e seen that a number of the plates 

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

 cxam])lc, tlie ectoturbiuals arc four in number. The fii'st is obliquely 

 placed li\)m above downwarel, and within outward. Two conspicuous 

 convolutions arc present at the distal end, tlic lower one <>f which alone 

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

 sesses a single convolution, which is directed outward. Tiie lliird and 

 fourth are very short, biconvolute, and directed upward and forwanh 

 None of the ectoturbiuals appear on the longitudinal surface of the 

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

 rected forward and upward, and neai'ly touches tlie median convolution 

 of the first ectoturl)inal. It is biconvolute, l)ut the parts are sh(jrt 

 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 

 lii'st ])late, lint they are less conspicuous. The third and remaining 

 ])late is tlie smallest of tlie 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. Tiie nasoturi)iiial is seen in the section as a minute 

 iion-convdlute structiu'e, intci'mediatc l)etwecn tiio two sets of plates. 



The endoturbiuals are always ai'ranged in tiers one above another. 

 All originate fnnn tlie lateral surface. In the do;/ (Plate I. fig. 2) the 

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

 the bottom of the nasal cliamber as far as the meso-ethmoid, along 

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

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

 plates tend to unite anteiiurly. Tlius two to tliree plates unite to form 

 the nasoturbiual in tlie r/07. 'I'he lower endoturbinal jilates unite in 

 ii-oiit b}' broad, thin pLites. These, taken collectively, constitute tlie 

 transverse lamina of Sti-auss-Din-ckhcim. It is constantly present, 

 stretching across the septoturbiual space to the vomer, against whicli 

 it rests. 



The ectotiirbi'ud plates may Ik; rudimentary or absent. They would 



