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On compare trois méthodes différentes de calculer l'intervalle de confiance de la pente de l'axe majeur d'une distribution normale bidimensionnelle, et on applique ces méthodes à des exemples portant sur l'allométrie et sur la composition chimique de l'urine humaine. L'intervalle dérivé de l'estimation du coefficient de corrélation entre les axes principaux hypothétiques paraît généralement préférable à celui que donne une méthode applicable aux grands échantillons ainsi, qu'à celui de la pente de l'axe majeur réduit.
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An attempt is made to distinguish between mathematical, statistical, and biological properties of weight-length curves. The available data for turtles (Reptilia : Testudines) are presented and discussed. Emphasis is made of certain difficulties in estimating total size of an animal from weight or from length. Special reference is given to the use of these measures in ecological studies.
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The systematics of the genus Geoemyda are poorly known. The genus, known from eastern Asia and from central and northern South America, is represented in Mexico by three species: G. rubida, G. pulcherrima, and G. areolata. Dangers in the use of the clinal concept in interpreting the taxonomy of these forms are discussed.
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An analysis is made of sexual dimorphism in a sample of 60 snapping turtles collected in southern Quebec and Ontario during the summer of 1956. In our sample males constitute the larger sex. There is no demonstrable sexual dimorphism in shell dimensions nor in head width. The only reliable external indicator of sex found is the distance from the plastron to the cloaca. This is relatively longer in males. In turtles less than 200 mm in carapace length, this is not reliable. Maturity occurs in both males and females at about this size. The sex ratio in our sample is …
