39° 



MANUAL OF ZOOLOGY 



may be nearly completely cartilaginous {Hcxanchus and 

 Heptanchus), but usually the centra are strengthened by 



Fig. 233. — Skeleton of sting-ray (UrolophUS testaceus), ventral view, a.v.p, 

 anterior vertebral plate; bas. br, basi-branchial plate; br. i-br. j, branchial 

 arches. The branchial rays are represented as having been removed, the round 

 dots indicate their articulations with the arches cl, skeleton of clasper; h, m, 

 hyomandibular; Jty. hyoid arch; lab, labial cartilage; lig, ligament connecting 

 the hyomandibular with the palato-quadrate and Meckel's cartilage; ntck, 

 Meckel's cartilage; nts. fit, mesopterygium ; mt. f>t, metapterygium of pectoral 

 fin: ml.pt', metapterygium of pelvic fin; ?ias, nasal cartilage; pal, palato- 

 quadrate ; pect, pectoral arch; pi, pelvic arch; pro.pt, propterygium; sp, spiracu- 

 lar cartilage. 



