. A manual of zoology. Zoology. 496 CHORDATA. upper ends are frequeiitl_v toothed and, in chewing are opposed b)' the rudimentary last arch, on wliich account these are spoken of as the superior and inferior pharyngeal hones. The anterior visceral arches are greatly diiferent in cartilaginous and bony fishes. In the former (hg. 546) the pterygocjuadrate {J>q) and the jMeckelian cartilage (.!/</) bear teeth and oppose each other in biting. In the bony fishes (fig. 547) the teeth of the lower jaw oppose the tooth-bearing elements, premaxillary and maxillary, of the maxillary series, while
. A manual of zoology. Zoology. 496 CHORDATA. upper ends are frequeiitl_v toothed and, in chewing are opposed b)' the rudimentary last arch, on wliich account these are spoken of as the superior and inferior pharyngeal hones. The anterior visceral arches are greatly diiferent in cartilaginous and bony fishes. In the former (hg. 546) the pterygocjuadrate {J>q) and the jMeckelian cartilage (.!/</) bear teeth and oppose each other in biting. In the bony fishes (fig. 547) the teeth of the lower jaw oppose the tooth-bearing elements, premaxillary and maxillary, of the maxillary series, while the pterygoquadrate ele- ments—the palati)ie and the series of pterygoids—are the antagonists of the hyoid. In the elasmobranch type the two halves of the pterygo- i^ ff/!j{. po tr. Fig. 546.—Cranium, nsceral arches, and part of vertebral column of Muslchis vulgaris. ao, antorbital process; co, copula; gp, foramen for glossopharvngeal; H, otic capsule and hyoid; Hm, hyomandibular; ic, inlercalarc; ild. mandible (.Meckel s cartilage"); A^, nasal capsule; o, optic foramen; oh, neural arch; /)<), poslorbital process; Pq, pterygoquadrate; ps, spinous process; R, rostrum; r, ribs; tr, trigeminus foramen; V, vagus foramen; i-S, visceral arches; i, labial; 2, mandibular; 3, hvoid; 4-S, gill arches. quadrate meet by symphysis in the middle line; in the others thev are separated by the floor of the skull. A second characteristic of the bony fishes is already outlined in the cartilaginous fishes: the modification of the hyomandibular to a suspensor of the jaws. In the elasmobranchs (especially the skates) the parallelism of hyoid and mandibular arches is lost, the hyomandibular separating from the hyoid and attaching itself to the hinge of the jaws. In the teleosts the hyomandibular is thus brought in connexion with the quad- rate, and hes Ijetween it and ihe cranium, the joint being thus indirectly supported from the cranium, a bone, the sympleelic (known only in fishes) h
Size: 2520px × 992px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
