. The Cambridge natural history. Zoology. 444 FISHES CHAP. Scarcely anything is known of the habits of the JSTotidanidae and the Ohlamydoselachidae. It is evident that they are closely- related forms, and from the unusual number of their gill-clefts and branchial arches, and the condition of the vertebral column, it is also obvious that they are the most archaic of modern Fig. 252.—Chlainydoselachus anr/ioineus. (Fi'om Giintlier.) Fam. 3. Heterodontidae (Bullhead Sharks).—Head large and high, with a blunt snout projecting but little in front of the small and almost terminal mouth,
. The Cambridge natural history. Zoology. 444 FISHES CHAP. Scarcely anything is known of the habits of the JSTotidanidae and the Ohlamydoselachidae. It is evident that they are closely- related forms, and from the unusual number of their gill-clefts and branchial arches, and the condition of the vertebral column, it is also obvious that they are the most archaic of modern Fig. 252.—Chlainydoselachus anr/ioineus. (Fi'om Giintlier.) Fam. 3. Heterodontidae (Bullhead Sharks).—Head large and high, with a blunt snout projecting but little in front of the small and almost terminal mouth, and with prominent supraorbital crests. Trunk thick-set and somewhat trihedral, covered with fine shagreen. ISTostrils ventral but nearly terminal, with oro- nasal grooves. Spiracles small, beneath the eyes. Two dorsal fins, each with a spine in front, the first opposite the interval between the pectorals and pelvics, the second in front of the anal. Vertebral centra asterospondylic when fully developed. Palato-quadrate cartilages with an extensive articulation with the sides of the preorbital regions of the cranium, the normal sus- pensoria of a hyostylic skull (hyomandibular cartilages) taking little share in their support. Dentition similar in both jaws. Teeth at the symphyses numerous, small, and conical, furnished with three' to five cusps in the young; those behind broad and pad-like, arranged in oblique rows, the teeth forming the tvFO middle rows being much larger than those in the front or behind. Living species, oviparous. Egg-cases large, with an external spiral lamina (Fig. 245). About four species belonging to one genus, Heterodontus (= Cestracio7i) (Fig. 253), or possibly to two, represent this dwindling family. All are inhabitants of the Pacific Ocean (J'apan, Amboyna, Australia, the Galapagos, and the Californian coast of North America). Little is known of their habits. They feed. Please note that these images are extracted from scanned page images that may
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
