Evolution of Animals 477 



(7) The mandible consists of three pieces, and articu- 

 lation is with the quadrate bone. 



(8) The vertebrse are pseudo- or in highest urodeles 

 opisthocoelous. 



(9) There are abdominal ribs, or these fuse to form 

 a sternum that joins Tvith the coracoid. No distinct 

 coracoids however are formed. 



(10) The heart consists of a ventricle, two auricles, 

 and conus with one row of valves. 



(11) The aortic arches are strictly symmetrical. 



(12) The red blood corpuscles are nucleated, oval, and 

 biconvex. 



(13) The lungs are simple and paired, at times Tsath 

 trachea and cartilages. 



(14) The vagus is the last cranial nerve, and the hypo- 

 glossal is a true spinal nerve. 



(15) There are kidneys with persistent nephros tomes. 



(16) Most are oviparous, a few only are viviparous. 



(17) There is no amnion, but the allantois is feebly 

 represented by a swelling of the cloaca that is a urinary 

 bladder. 



In Reptilia. 



* (1) The skin develops scales, shields, warts, or scutes, 

 never hairs; it is non-glandular; the sensory nerve endings 

 are embedded; pigment cells are occasional. 



(2) The limbs are tetrapodous and four- to j5ve-dactyl, 

 or have been absorbed. When digital reduction occurs, 

 digit V always disappears first, followed by digit I. 



(3) Temporary gill clefts are formed, but lungs alone 

 aerate the blood. 



(4) Sense organs of the lateral lines are rare or absent. 



* (5) The skull articulates with the first vertebra by 

 one basi-occipital condyle. 



(6) An auditory collumelar apparatus fits into the fen- 

 estra ovalis. 



* (7) The mandiljle consists of six pieces, and articu- 

 lation is with the quadrate bone. 



