A manual of the anatomy of vertebrated animals / by Thomas H. Huxley.

Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: A manual of the anatomy of vertebrated animals / by Thomas H. Huxley. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    The two remaining groups are very peculiar; bnt I con- fess I do not see upon what ground they can be regarded as of ordinal value. 5. The Lopliobrancliii.—The body is covered with bony plates. The ventral fins are almost always absent. The inferior pharyngeal bones are distinct. The branchial ]3i0- cesses have a clavate form, being larger at the free than at the attached ends, and are in this respect lanlike those of any other fishes. {Pegasidce, SyngnathidcE.) 6. The Plectogncdlii.—The body is covered with plates or spines. The ventral fins are absent, or represented only by spines. The inferior pharyngeal bones are distinct. The premaxillse and, usually, the hyomandibular, are im- moveably united with the skull—a character of rare occur- rence among other fishes. {Gymnodontidce, Ostraciontidce, Bcdistidce.) The greater number of Teleostei are marine. 'No Anacan- tliini, Plectogncdlii, or Lophohranchii, and only one family of Pharyngognathi (the Chromidce), inhabit completely fresh water. Comparatively few Acanthopteri are fluviatile. On the other hand, by far the greater number of the Physostomi are, either temporarily or permanently, freshwater fish. If the LeptolepidcB {Thrisso'ps, Leptolepis, Tharsis) are Ganoids, the Teleostei are not known before the Cretaceous epoch, when both Physostomi and Acanthopteri make their appearance, under forms, some of which (e.g., Beryx) are generically identical with fish living at the present day. YI. The Dipnoi.—The Mudfishes of the rivers of the east and west coasts of Africa and of eastern South America are nearly transitional forms between the Pisces and the Amphibia. The eel-like body, covered with overlapping cycloid scales, tapers to a point at its caudal extremity, and is provided with, two pairs of long, ribbon-like, pointed ex- tremities, and with a caudal fin. The spinal column consists of a thick notochord, invested by a cartilaginous sheatb, without any osseous or cartila-