674 



Comparative Morphology of Chordates 



extends a thin cartilaginous plate derived from the cartilaginous capsule 

 (Fig. 115) which, at an early embryonic stage, encloses the nasal 

 cavity. Eventually these turbinal plates ossify (not always completely) 

 and become more or less intimately joined to adjacent bones which 

 meanwhile have developed around the nasal cavity. The uppermost, 

 the nasotvirbinal, joins the nasal bone which roofs the cavity. The 

 lowermost, the maxilloturbinal, becomes attached to the maxillary 

 bone which abuts upon the ventrolateral region of the nasal wall. 

 Between nasoturbinal and maxilloturbinal, but more or less posterior 

 to them, are developed a varying number of ethmoturbinals. They 

 are continuous with the ethmoid bones which form the lateral walls 



ECTOTURBINALS 



SUPERIOR 

 CONCHA- 

 (TURBINAO. 



Fig. 505. Diagrams of cross sections of the nasal 

 passage in (A) ruminant and (B) man, showing the 

 contrast in the number of turbinal bones. (Cour- 

 tesy, Neal and Rand: "Chordate Anatomy," 

 Philadelphia, The Blakiston Company.) 



of the nasal cavities. The single turbinal (concha) of reptiles (Fig. 367) 

 is a maxilloturbinal. 



In the adult these primary turbinals usually extend nearly across 

 the cavity (Fig. 505). They are approximately parallel to each other 

 and to the floor of the cavity. Each turbinal is more or less elaborately 

 curled spirally (as a sheet of paper might be rolled), but always with 

 some space between adjacent turns of the spiral. These rolled turbinals 

 are often called "nasal scrolls." In some cases a turbinal arising 

 from the nasal wall as a single plate divides distally into two, which 

 diverge and curl in opposite directions (Fig. 505). In the most elaborate 

 systems, the spaces between adjacent major or primary turbinals are 

 occupied by lesser secondary turbinals and there may be even 

 smaller tertiary scrolls between the secondaries (Fig. 505). Because 

 their scrolls occupy the more nearly median or deeper part of the 

 cavity, the primary turbinals are called endoturbinals. The lesser 



