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Geographic variation of 11 measurable cranial traits was studied on a set of 37 local samples of the Libyan jird, Meriones libycus, over its entire distribution area. MANOVA, cluster, canonical discriminant, and regression analyses were applied to consider both scalar and vector parameters of variation. It is shown that the Libyan jird is divided craniometrically into tree principal clusters, African, SWN Caspian, and main Asian ones, which differ basically by auditory bulla size (the least in SWN Caspian cluster) and incisive foramen length (the least in some subsamples of main Asian cluster). Auditory bulla size is shown to be negatively, though not very strongly, correlated with the aridity index. However, the SWN Caspian cluster is characterized by much smaller bulla than it is predicted by the regression with climatic parameter. This might be explained by some historical causes according to which a small size of auditory bulla in the jirds of that cluster reflects retention of the ancestral condition. It is suggested that subspecies M. l. caucasius from Azerbaijan is most conspicuously differentiated by cranial morphology, but its taxonomic relation to M. l. eversmanni from N Caspian region needs further clarification. The method of vector analysis of geographic trends within large portions of the areas of widely distributed species, such as M. libycus, seems to be useful in providing additional important information concerning biological specificity of respective territorial groupings.

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A number of series of tooth anomalies of the same type in three carnivore species is described. The most interesting are the following: supernumerary teeth near Pm<», which appearance may be accounted by atavismus; reduction of M 2 , that demonstrates the possible way of demolarisation of this tooth under the shortening of maxillary toothrow; the splitting of the Pm 1 -Pm 3 , that shows an influence of morpho-genetic field upon development of the tooth under abnormal condition. Generalized scheme of possible ways, by which the appearance of supernumerary teeth in mammalian tooth row may be accounted, is discussed. I. INTRODUCTION AND METHODSome interesting dental anomalies were found during an examination of the skulls of the fox Vulpes vulpes (Linnaeus, 1753), the arctic fox Alopex lagopus (Linnaeus, 1758) and the grey fox Urocyon cinereoargenteus E r x 1 e b e n, 1777 in the collections of the Zoological Museum, Lomonosov University in Moscow, the Institute of Zoology, U.S.S.R. Academy of Sciences, and the Biological Institute, Siberian Centre of the U.S.S.R. Academy of Sciences.The present paper contains a detailed description of these anomalies and an analysis of quantitative relations, which permit a better grounded discussion of the origin of dental anomalies.In order to characterize the teeth quantitatively, the following measurements have been taken: (1) the overall tooth height, from the tip of the root to the highest point of te crown, (2) the length and (3) width of the crown, measured by the cingulum, and (4) the length and (5) height of the crown top, measured using a micrometer eye-piece, the straight line connecting the points where the mesodistal ridge merges with tl)2 cingulum being assumed as the crown basis. On the other hand, to characterize the position of a tooth in the tooth-row a projection was produced using a camera lucida and the angle between the meso-distal axis of two neighbouring teeth was measured. The meso-distal axis of a tooth is the straight line that connects the remotest mesial and distal points of the alveoli of [507]

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