. Outlines of zoology. Zoology. THE SKELETON. 485 divided into distinct regions, nor has it anything corre- sponding to the investing membrane bones, which in higher animals are added to the original foundations of the skull, nor do the visceral arches in the skate take part in forming the skull, which arises, as usual (see p. 431), from para- chordals, trabecule, sense capsules, etc. The visceral arches are primitively supports for the wall of the anterior part of the food canal, but at least two of them are much modified in connection with the jaws. The upper jaw of the skate is a strong tra
. Outlines of zoology. Zoology. THE SKELETON. 485 divided into distinct regions, nor has it anything corre- sponding to the investing membrane bones, which in higher animals are added to the original foundations of the skull, nor do the visceral arches in the skate take part in forming the skull, which arises, as usual (see p. 431), from para- chordals, trabecule, sense capsules, etc. The visceral arches are primitively supports for the wall of the anterior part of the food canal, but at least two of them are much modified in connection with the jaws. The upper jaw of the skate is a strong transverse bar,. Fig. 204.—Side view of skate's skull. —After W. K. Parker. P., First labial cartilage; , nasal capsule; , antorbital; , palato-pterygo-quadrate; , Meckel's cartilage; , hyo-mandibular; , epi-hyat; , cerato-hyal; hypohyal ; A.^n1-5, hypobranchials; , cerate-branchial; , epibranchial; p-br*., first prebranchial; , inter-hyal; , meta-pterygold ; 2, 5, 7, foramina of exit of the corre- sponding nerves. formed from the union of two palato-pterygo-quadrate cartilages. The lower jaw is a similar bar formed from the union of two Meckel's cartilages. From the ear capsule to the articulation of upper and lower jaw there extends on each side a club-shaped cartilage, which connects the jaws with the skull, known as the hyo-mandibular or suspensorium. It is the upper half of the second arch. Attached to it is a slender four-jointed rod—the lower half of the hyoid arch. Then follow five branchial arches, each primarily four- jointed, forming the framework of the gill-bearing Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
