RODENTS OF LIBYA 65 



considered are the implications of physiography and geography and 

 their roles in generating evolutionary developments and morphological 

 differences. Plausible avenues of dispersal are considered whenever 

 affinities and relationships with other populations are held unac- 

 countable. Range extensions are also included here. 



8. Ecological observations: This section provides information on 

 behavior and some aspects of natural history with emphasis on habitat 

 preferences. Considerable detail is given to the types of plants and 

 the nature of the substrate forming the various habitats. 



9. Description of new subspecies: The format for describing new 

 subspecies is identical to that used for the accounts of recognized 

 subspecies except the newly proposed subspecific name is followed by 

 the designation of the holotype. Data relating to the holotype are 

 recorded in the following sequence: Sex; an indication as to whether 

 the holotype represents skin, skull or both; museum of repository 

 (USNM = United States National Museum); catalog number; exact 

 collecting locality; date of collection; name and original field number 

 of the collector. 



10. Analysis of variation and the diagnostic characters of the 

 species and subspecies: In an effort to determine the extent of indi- 

 vidual and geographic variation within the various species and sub- 

 species of Libyan rodents and to ascertain the measurable characters 

 which distinguish them, specimens were selected from localities 

 which represented the most typical representatives of the particular 

 taxon and were then treated statistically. In some instances, on the 

 specific level, it was necessary to pool specimens from several localities 

 in order to increase sufficiently the size of the sample and thus in- 

 crease statistical reliability. Generally, however, the analyses are 

 based on specimens from a single locality. In determining the amount 

 of morphological divergence and variation within and between sub- 

 species, paratypical or topotypical specimens were used whenever 

 possible. In all of the analyses and comparisons, the sexes have been 

 treated separately to prevent erroneous conclusions arising from 

 sexual dimorphism. 



Before taxonomic variation could be determined for a population 

 of rodents, the amount of nongeographic variation had to be taken 

 into account. In this latter category are included random genetic 

 variation inherent in the gene pool of the species or subspecies and 

 the differences resulting from growth, age, sex, seasonal changes, 

 pathological conditions, and other kinds of variation related to known 

 stimuli. To prevent misleading interpretation of the variation associ- 

 ated with geographical distribution, extreme care was taken to insure 

 that all specimens in the sample were of comparable age, and those 

 suspected of showing seasonal characters, pathological conditions, or 



