Cursory examination of skulls of the _callotis_ group and the _californicus_ group indicates that the prepalatal spine (the part of the palate which extends anteriorly toward the vomer) is longer in _L. californicus_ than in _L. callotis_, _L. gaillardi_ and _L. alleni_. In this feature, _L. altamirae_ agrees with _Lepus californicus_ and differs from members of the _Lepus callotis_ group. Furthermore, the newly named _L. c. curti_, in color of ear and color of nape, is intermediate between _L. altamirae_ and _L. c. merriami_. Consequently, _Lepus merriami altamirae_ Nelson, it seems, should stand as _Lepus californicus altamirae_. Mention should be made here of the view of Shamel (Proc. Biol. Soc. Washington, 55:25-26, May 12, 1942) that the _californicus_ group should be divided into two groups (each group possibly amounting to something more than a species and something less than a subgenus) on the basis of a white rump and complex infolding of the enamel layer of the front of the first upper incisor _versus_ a dark rump and simple infolding of the mentioned layer of enamel. He placed _Lepus californicus merriami_ Mearns, among other subspecies, in a group different from the one in which he placed several other subspecies of _Lepus californicus_. Specimens (skulls with accompanying skins) of the species _Lepus californicus_ in the Biological Surveys Collection of the United States National Museum, representative of a gradual transition from the dark rump and simple fold in the enamel to the white rump and complex fold in the enamel are as follows: _L. c. deserticola_, No. 29733/41808, Paharanagat Valley, Nevada; Nos. 117463 and 156744, Beals Spring, Arizona. _L. c. texianus_, No. 24635/32031, Springerville, Arizona; No. 97453, Roswell, New Mexico; No. 118751, Toyah, Texas; No. 118749, Valentine, Texas; and No. 108700, Terlingua Creek, Texas. In the continuously distributed species _Lepus californicus_, along the northwest to southeast line provided by the localities of occurrence listed immediately above, there is a gradual transition from one kind of fold to the other kind and from one color of rump to the other color. It is clear that Shamel (_op. cit._) was in error in his conclusions; the kinds of black-tailed jack rabbits to which Shamel (_op. cit._) applied the name _Macrotolagus_ should stand as given below. Correct names: _Lepus alleni alleni_ Mearns _Lepus alleni palitans_ Bangs _Lepus alleni tiburonensis_ Townsend _Lepus gaillardi gaillardi_ Mearns _Lepus gaillardi battyi_ J.A. Allen _Lepus callotis_ Wagler _Lepus flavigularis_ Wagner _Lepus californicus altamirae_ Nelson _Lepus californicus melanotis_ Mearns _Lepus californicus merriami_ Mearns _Lepus californicus asellus_ Miller _Lepus californicus festinus_ Nelson _Lepus californicus texianus_ Waterhouse MEASUREMENTS (IN MILLIMETERS) OF ADULTS OF TWO SUBSPECIES OF LEPUS CALIFORNICUS