. Zoology : for students and general readers . Zoology. COMPOSITION OF THE SKULL. 399 ing gill-slits or spiracles, but are closed in the higher Verte- brates. As a rule, the skull is symmetrical, exceptions being found in the flounders and the bones about the nose of cer-. i'i?. 386.—Skull of the Lion. 2, occipital condjie ; 7, Parietal bone and sagittal crest ; 8, ; 2?', squamosal bone ; a?, zygi>matic arch ; 26, malar bone ; 11, ttontal bone ; 12, post-orbital process; 15, nasal bone; 21, maxillary bone; 22, premaxillary bone ; 32, mandible ; 3, occipital crest; c, canine t
. Zoology : for students and general readers . Zoology. COMPOSITION OF THE SKULL. 399 ing gill-slits or spiracles, but are closed in the higher Verte- brates. As a rule, the skull is symmetrical, exceptions being found in the flounders and the bones about the nose of cer-. i'i?. 386.—Skull of the Lion. 2, occipital condjie ; 7, Parietal bone and sagittal crest ; 8, ; 2?', squamosal bone ; a?, zygi>matic arch ; 26, malar bone ; 11, ttontal bone ; 12, post-orbital process; 15, nasal bone; 21, maxillary bone; 22, premaxillary bone ; 32, mandible ; 3, occipital crest; c, canine teeth ; p'^, second pre- molar ; nil, molar tooth.—After Owen. tain whales and porpoises. The base of the skull is perfo- rated for the exit of the nerves proceeding from the base of the brain, and the hinder bone [ocvipid) is perforated {fora- men magnum) for the passage of the spinal cord from the medulla oblongata. It is probable that there is a general parellelism between the head of Insects and Vertebrates, tp thnt while the Fig. 387.—Skull and visceral skeleton of a ^iacAian , xnat wniie uie (^,^|^^j^^ ^^^ occipital region; la, wall of the laby- head of insects, for rinth : elh, ethmoidal region ; n, nasal pit; a, ftrst, b. e, second labial cartilage ; o, suoerior, n, inlerior portion example, consists OI of the mandibular arch/. ; //., hyoid arch; f- . 1 „ (1-6), branchial arches.—After Qegenbaur. a certain number or segments, homologous with tliose of the rest of the body, and with mouth-parts homologous with the limbs ; tha,t the skull is also segmented, and an expansion and continuation of the vertebral column. Gegenbaur even maintains tiiat the various arches of the head are homologous with the 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 Packard, A. S. (Alpheus
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
