. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 74 ANATOMY OF VEETEBRATES. proceeds in a sjiecial direction, to stamp the species with its own distinctive and peculiar character: in the Brancliiostoma by the articulated cartilaginous labial arch and its numerous filaments; and in the proper Myxinoids and Lampreys by the formation of the complex system of lateral and labial cartilages ; or by the modification of the palatine, maxillary, and hyoid rudiments, in relation to the suctorial function of the mouth. In the Sturgeon (Adpenser) fig. 62, the growth of cartilage h
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 74 ANATOMY OF VEETEBRATES. proceeds in a sjiecial direction, to stamp the species with its own distinctive and peculiar character: in the Brancliiostoma by the articulated cartilaginous labial arch and its numerous filaments; and in the proper Myxinoids and Lampreys by the formation of the complex system of lateral and labial cartilages ; or by the modification of the palatine, maxillary, and hyoid rudiments, in relation to the suctorial function of the mouth. In the Sturgeon (Adpenser) fig. 62, the growth of cartilage has inclosed the whole of the brain-case, f, (j, and blended with its walls the ear-capsules: in advance of this it developes protective cavities for the now well-developed eyes and doul^le nasal sacs : the orbit, i, being divided from the nostril, U, by tlie ridge, 2, and Ijoth sup)ported by a ' \'fimerine' basis, ff" : beyond which the cranium is continued forward as a long pointed rostrum. The cartilaginous pedicle susj^endlng the palato-maxiilary apparatus is. Fore part uf ciiaoskelcLuu, Sturgeon divided into three piieces; the epitympanic, ilx m, the mesotvm- panic, ib. n, and the hypotympanic, ib. 26. The latter supports the j)alatine vault, 20, with wliich the pterygoids, se, are confluent; the maxillary, 21, the premaxUlary ljone,'2"2, the lalnal cartilage^ 74, and the mandible, 32. All these parts of the edentulous suctorial mouth are very small in proportion to the size of the bead and entire fish; and they are the only ossified parts of the end(3skeleton. The premaxillary is a subtriangular plate, jomed by ligament to its fellow, trenchant anteriorly, and extending in an arched form to the mandible. The mandible, 32, articulates by a concavity to the ptervgoid and premaxillary, and consists of a single piece, united to its fellow by a ligamentous sym])liysis. The mouth of the Sturgeon opens upon the under surface of tlie head, and is protruded and retracted
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