Xin 



PHYLUM CHORDATA 



441 



surface or symyihysis, while behind they diverge like the limbs of a 

 letter V. In each ramus is a horizontal portion (anterior), which 

 bears the teeth, and a vertical or ascending portion, on which is 

 the articular surface or condyle (cond.) for articulation with the 

 glenoid cavity of the squarnosal ; in front of the condyle is the 

 compressed coronoid process. The angle where the horizontal and 

 ascending processes meet gives off an inward projection or angular 

 process (ang. pro.). 



The liyoid consists, in addition to the separate vestigial stylo- 

 hyals already mentioned (p. 438), of a stout thick body or basi-hyal, 

 a pair of small anterior cornua or cerato-hyals, and a pair of long 

 backwardly directed cornua or thyro-Jiyals. 



The auditory ossicles, contained in the cavity of the middle ear, 



mortb 



p.m 



tybul par.oc 



-/ p,sph 



FIG. 1094. Lepus cuniculus. Skull in longitudinal vertical section. The cartilaginous 

 nasal septum is removed, a. sph. alisphenoid ; e. oc. exoccipital ; e. tb. ethmo-turbinal ; 

 tth. ethmoid ; ft. fossa for flocculus of brain ; i. incisors ; mx. tb. maxillary turbinal ; n. tb. 

 naso-turbinal ; pal', palatine portion of the bony palate ; peri, periotic (petrous portion) ; 

 p. sph. pre-sphenoid ; sph. f. sphenoidal fissure ; s.t. sella turcica, or depression in which the 

 pituitary body lies ; I. point at which the olfactory nerves leave the skull ; II. optic 

 foramen ; V. mn. foramen for mandibular division of trigeminal ; VII. for facial nerve ; 

 VIII. for auditory nerve ; IX, X, XI, for glossopharyngeal, vagus, and spinal accessory; 

 XII. for hypoglossal. Other letters as in Fig. 1093. (From Parker's Practical Zoology.) 



and cut off from the exterior, in the unmacerated skull, by the 

 tympanic membrane, are extremely small bones, which form a 

 chain extending, like the columella auris of the Pigeon, from the 

 tympanic membrane externally to the fenestra ovalis internally. 

 There are three of these auditory ossicles the stapes, which corre- 

 sponds to the columella of the Pigeon ; the incus, and the malleus, 

 the latter with a slender process (processus gracilis) : these are said 

 to be derived respectively from the quadrate and articular elements 

 (q.v.) of lower vertebrates. In addition there is a small disc-like 

 bone, the orbicular, which is attached to the incus. 



The elements of the pectoral arch are fewer than in the Lizard. 

 There is a broad, thin, triangular scapula, the base or vertebral edge 

 of which has a thin strip of cartilage (the supra-scapular cartilage) 

 continuous with it. Along the outer surface runs a ridge the 

 spine ; the spine ends below in a long process the acromion process 



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