Volume 1

The Fauna of British India, including Ceylon and Burma / edited by W.T. Blanford. Fishes. VolsI & II / by Francis Day.

Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: The Fauna of British India, including Ceylon and Burma / edited by W.T. Blanford. Fishes. VolsI & II / by Francis Day. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    the four anterior ones are Uned in front with parallel rows of adherent gills, whilst in the fifth these processes are found_ solely on its proximal side. Water taken in by the mouth for respn-atory pui-poses passes backwards through the pharyngo-branchial slits into these sacs, from whence it emerges by the external gill- onenings or stigmata. The scapular arch, which is suspended to the front part of the vertebral column, divides these respn^atory sacs from the abdominal cavity. Although opercular pieces are absent, cartilaginous rings are sometimes present surrounding the gill-openings. _ . . ,, ■ i . The size to which these fish attain is not an invariable index to their character, which is better shown by an examination of the teeth with which they are armed. Some powerful forms have small teeth, whilst the obtuse teeth of particular genera are more calculated for crushing shells and Crustacea than for waging war with other fishes. The scales are peculiar, being generally small papillaj that have a coating of enamel: this, under the designation of shagreen, is sometimes employed in certain trades, as for coveruig small boxes or the scabbards of swords, or even for smoothing down wood. The tail-fin is flexible and of great power, terminating much like the blade of an oar, and givmg the bearer great facilities in pursuit; when seizmg their prey, if it is large, sharks generally tui'n on one side. When breeding, a congress takes place between the sexes, the arrangement of the sexual organs being somewhat similar to what obtains among the higher vertebrates. The male organs are com- pact, placed far forwards in the abdominal cavity, while attached to the ventral fins are elaspers which have intromittent functions. In the females, different parts of the oviduct may be functionally modified, for although the ova are fertdized within this oviduct, the development of the young is not invariably carried out on the same plan, some being perfected prior to extrusion, while in others the ovum is encased in a horny covering and so deposited t® sea. In such forms as produce their young alive, a modified placenta exists. GeograpUcal Distribution. Sharks are spread throughout the seas and estuaries of cold, temperate, and tropical regions, bemg most numerous in the last; and some ascend rivers even far beyond the influence of the tides *. They are common along the coasts ot India, and some species have a wide range, although they do not appear to descend to any great depth. They seem to scent blood or offal from long distances, but their carrying off human prey is * Not only Blmrka but saw-fishoa ofciisionally reside in pieces of fresli water, when the communioiition with t.ho sea has been cut off. Professor Meyer (' Nature,' Doc. 30,1875) remarked on this subject that an accurate coniparison (between marine and freshwater forms) showed no difference at all, and therefore the changed couditions seem to have liad no influence on the external features of the .species.