"•^Bl 



SAOCOMYID^— CHAKACTKUS OF TUE FAMILY. 



491 



a subgenus of Perognathm, upon certain obvious and eligible external char- 

 acters alone. But examination of the skull, which, it seems, that author did 

 not make, has satisfied me that the cranial peculiarities arc fully up to a cur- 

 rent generic mark. Cricetodipus, in fiict, makes a decided step away Irom 

 Perognathus in tiie direction of Dijjodomi/s, though still falling far short of 

 the exaggerated peculiarities of the latter. 



Family SACCOMYID^. 



< Saooomyina, Wateruocse, Nat. Hist. Muuidi. ii, 1S46, 8. (As a gronp of Uuridw. Inoladed the Oeomyid(t, 



now miulo a separate family; equivalent to the " superfamily " ;8accomjfo<<iea of Gill, 1972.) 



< Paeudotiomida;, Gervais, " Diet. Univ. d'Hist. Nat. xi, 1848." (Family Equivalent to the Saaxmyina 



of Waterhonsc.) 



< Saccomyiia, Lilljeboro, Syst. (Efv. Gnag. Diiggdj. 18C6. (Family. Equivalent to Saooomyina of 



Waterbouso.) 

 = Saooomyina, Baird, Mamm. N. Am. 1857, 404. (Subfamily of Sacoomyidw, which, with this author, 



included Otomyidoe, Bainl's family Saccomyida being equivalent to Sacromyinn, Waterh.) 

 = Saocomyinw, Gray, Proc. Zoiil. Soo. 1868, 19U, (Spoken of as a " family ", though terminology indicates 



subfamily.) 

 = Saccomyidw, Gill, Arraug. Fam. Mamm. 1872, 21. (Family.) 

 = Saocomyidw, CouES, Proc. Phila. Acad. 187.1, 2/4. (Family.) 

 = fl«i(«r»myina!, Alston, Proc. Zoiil. Soc. Lend. 1876, 88. (Subfamily. Equivalent to Saooomyina ot 



Baird and Saccomyida of Gill and Cones.) 



Chabs.* — Skull light, thin, and papery, with few, if any, decided angles 

 or ridges ; rostrum elongate, attenuate, and tapering ; nasals projected beyond 

 incisoto. Intermastoid width not less than the interzygomatic, sometimes 

 much grnate"". Interorbital space much wider than the rostrum. Occipital 

 region formed largely or mostly of the mastoids. Palatal surface nearly flat 

 and horizontal. No anteorbital foramen in a usual site, but a large, rounded 

 perforation of the side of the maxillary instead. Zygomata slender, depressed 

 in position, almost or quite abutting behind against the tympanic ; malar 

 thread-like. Adelicsitescroll-likelachrymal, easily detached. Frontal broadly 

 trapezoidal. Parietal broad, triangular or pentagonal. A large interparietal, 

 embraced betwixt forks of the occipital. Squamosal almost entirely restricted 

 to the orbit. Tympanic more or less inflated. Mastoid enormously enlarged 

 and bullous, mounting to the lop of the skull, and also forming much or most 

 of the occipital surface, the occipital bone itself being corres|)ondingly 

 reduced, and scarcely forming part of the general occipital surface. Petrosals 

 moderately inflated, their apices closely approximated or even in mutual con- 

 tact. Coronoid process of mandible slender, sloping, prickle-like, scarcely 



•Drawn from Perognalku», Cricttodtput, ond Dipodomyt; but tlu'rc is reason to believe that no 

 material modlflt'«tion of the phrase is n'(|uired to embrace /ix/«rOTii^ii— exmipting probably some of the 

 cranial features, especially those of the temiwral region. Siiccial rofcreuee is hod to autilhcsis with 

 Geomyida; 



