388 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
palate in Hystriz is broad and flat, and of uniform breadth; in Erechizon it 
is narrowed anteriorly, and rises abruptly in front of the molars, and between 
the molar series presents a prominent, central, ragged keel. Without 
going into a further comparison, it may suffice to state that the structure of 
the skull in the two forms differs markedly in nearly every detail. 
To the old Linnean genus Hystrix were for many years referred all the 
known Porcupines from both the Old and the New World. The group was 
first dismembered by M. F. Cuvier in 1822, who divided the Old World 
species into two groups, Hystrix and Acanthion,* and the-New World species 
into three, Hrethizon, Synetheres, and Sphingurus (‘‘Sphiggurus”). Brandt, in 
1835, called special attention to the cranial differences characterizing the 
Old World and New World species, and adopted Cuvier’s genus Hrethizon 
for the North American species, but united the two South American genera of 
Cuvier into the single genus Cercolabes, which groups have since been com- 
monly retained, with the limitations and names given by Brandt. Cercolabes, 
however, seems divisible into two generic groups, for which Cuvier’s prior 
names should be retained.t Chetomys was established by Gray in 1843 for 
the Hystrix subspinosa of earlier authors. 
The genus Erethizon is confined to the middle and northerly portions of 
the North American continent, and is represented by a single species, divisi- 
into two easily distinguished geographical varieties or subspecies. 
ble into two easily distinguished geographical varieties or subspeci 
ERETHIZON DORSATUS (Linn.) F. Cuvier. 
Var. DORSATUS. 
Canada Porcupine. 
Hystrix dorsata LiNN., Syst. Nat., ed. x, i, 1758, 57; ed. xii, i, 1766, 76—ForsTER, Phil. Trans., lxii, 
1772, 374.—ERXLEBEN, Syst. Reg. Anim., 1777, 345.—GMELIN, Syst. Nat., i, 1784, 119.— 
SCHREBER, Siiuget., iv, 1792, 605, pl. clxix.—Suaw, Gen. Zool. Mam,, ii, 1601, 13, pl. exxv.— 
KuAL, Beitriige zur Zoologie, 1820, 70.—DrEsMarest, Mam., 1822, 345.—J. Sabine, Franklin’s 
Journey to the Polar Sea, 1823, 664.—Cozzens, Ann. N. Y. Lye. Nat. Hist., i, 1823, 191.— 
Haran, Fauna Amer., 1825, 190.—GopMan, Amer. Nat. Hist., ii, 1826, 50.—Grirriry’s Cuvier 
ili, 1827, 206; v, 1827, 263.—Fiscnmr, Synop. Mam., 1829, 368.—EmMons, Quad. Mass., 1840, 
71.—THOMPSON, Hist. Vermont, 1842, 47—AuDUBON and BACHMAN, i, 1843, 277, p]. xxvi. 
Erethizon dorsatus F. Cuvier, Mém. du Mus., ix, 423, pl. xx, figs. 1, 2,8 (skull and molar).—Branpt, Mém. 
Acad. St. Pétersbourg, 1835, 387—WarerHouss, Nat. Hist. Mam., ii, 1848, 438.—GirBeL, 
Sauget. 1855, 478.—WaGNER, Suppl. Schreber’s Siiuget., iv, 1844, 27 (in part)—Barrp, Mam."N. 
Amer., 1858 568.—ALLEN, Bull. Mus. Comp. Zodl., i, 1869, 235. 
* Acanthion, although applied to species with the frontal region of the skull only moderately swollen, 
has not been considered by most later writers as generically separable from Hystrix, the second of tho 
two genera of Hystricine commonly recognized being Atherura, first characterized seven years later by 
M. G. Cuvier. 
t Alston (Proc. Zodl. Soc. Lond., 1876, 94) considers Synetheres and Sphingurus as being not generic- 
ally separable; he adopts Sphingurus as the tenable name of the group, and hence changes the name 
of the subfamily from Cercolabinw to Sphingurine, although Synetheres has the precedence in Cuvier’s 
memoir. Gervais, as early as 1852, used the name Synetherina as a subfamily name for the New World 
Porcupines, which name hence has many years’ priority over Sphingurine. 
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