On the classification of Mammalia / by Charles Girard.

  • Girard, Charles, 1822-1895.
Date:
[1851]
Catalogue details

Licence: Public Domain Mark

Credit: On the classification of Mammalia / by Charles Girard. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    third family, that of Delphinidce, seems to complete the progressive series in the development of teeth; for the latter exist here on both jaws, whence the name of amhidcntated cetaceans. The fourth family, that of HeterodontidcB, includes the narwhale or predentated cetaceans, and some other types in which the dentition is losing both its shape and its function. The Monodon (narwhale) is closely allied to Pho- cana (porpoise), whilst Hyperoodon comes nearer to DelpMnus. The other genera are deviations or reminiscences of the other families. Heterodonts, then, must follow the dolphins in a natural and serial classification. The order of Cetacea begins with the whales, and closes with heterodonts ; the real superior groups are those placed in the middle, the Delphinidae, which represent the normal cetacean type. They are the smallest of the order, and possess two fresh-water representatives, one closely allied to dolphins proper, the second bearing some far relations to Physeteridse (sperm-whale), and to the genus Hyperoodon of the heterodonts family. The morphology of the teeth in Cetacea is very interesting, and instructive in a philosophic point of view, when the relationships of this order with the Edentata are well understood. In the lowest type, teeth remain undeveloped; in the highest, they cover the whole sur- face of both jaws, but are of one kind : incisors, canines and grinding teeth are not known amongst cetaceans. This fact alone would ascribe to them an inferior rank amongst the normal groups of the class. § 4. The affinities of the so-called herbivorous cetaceans, or Si- renidas, with pachyderms, have been alluded to by several authors. In 1834 Fred. Cuvier* wrote the following remarkable sentence: The group of herbivorous cetaceans, composed of genera inti- malely connected together, are related to the pachyderms by the manati. And farther on (page 6) he remarks that they come nearer to pachyderms than to cetaceans. In 1838 they were definitively removed from the Cetacea, and actually placed amongst Pachy- dermatat. Upon this point, every naturalist now agrees. Sirenidse are the lowest grade among pachyderms : even if considered as parallel material strength is developed, and the muscular power increased to harmonize with the immensity of the element in which they live. Balcenidee, the lowest of the order, are likewise amongst the largest. * Histoire Naturclle des Cetac6s, p. 34. \ Owen, in Proceed. Zool. Soc., London.