4H MANUAL OF ZOOLOGY sect. 



The palato- quadrate cartilage is unossified ; but in relation 

 to its anterior portion is a palatine {PAL) membrane bone 

 and to its posterior portion a pterygoid (PTG) . The former 

 is a slender rod-like bone directed transversely on the lower 

 surface of the skull. The latter is a larger three-rayed bone, 

 having an anterior, an inner, and a posterior arm. The 

 posterior portion of the palato-quadrate cartilage, the quad- 

 rate or suspensorium (sits), connects the lower jaw with the 

 posterior region of the skull. Internally it is covered over 

 by the inner and posterior arm of the pterygoid ; externally 

 a hammer-shaped membrane bone, the squamosal (SQ) 

 is applied to it. The upper jaw is formed by three mem- 

 brane bones, the small premaxilla (PMX) in front, then 

 the long narrow maxilla (MX ) , and finally the short quad- 

 rato-jugal (QU.JU) which is connected posteriorly with 

 the quadrate. The mandible contains on each side a per- 

 sistent Meckel's cartilage as a sort of core, ossified at its 

 anterior end, outside which are two membrane bones. The 

 hyoid is a squarish plate of cartilage (b. hy) with two pairs of 

 processes (a. c. Ay, p. c. hy), the posterior of which is ossified. 



The scapula is ossified and is connected by its dorsal 

 edge with a supra-scapula (Fig. 247, S. SCP) formed partly 

 of bone, partly of calcified cartilage, and developed from 

 the dorsal region of the embryonic shoulder-girdle. The 

 coracoid (Fig. 249, Co) is also ossified, while the procora- 

 coid is represented by a bar of cartilage, having a membrane 

 bone, the clavicle ( CI) , closely applied to it. The supra- 

 scapula overlaps the anterior vertebra? ; the coracoid and 

 procoracoid are connected ventrally by a cartilage, the epi- 

 coracoid (Co'), which is in close contact with its fellow of 

 the opposite side in the middle ventral line, so that the 

 entire shoulder-girdle, like that of the dogfish, forms a 

 single inverted arch. 



