l. 2; Woodbury and Hardy, 1948:165,
figs. 9 and 10), and _polyphemus_ (personal observation).

[Illustration: PLATE 7

PLATE 7. _Gopherus flavomarginatus_ new species: _Top_--Dorsal and
ventral views of holotype (x 1/3); _Middle_--Lateral view of holotype
(x 1/3); _Bottom_--Head of paratype (USNM 61254) (x 1/2) and
antebrachium of holotype (x 5/6). Dark outline on plastron of holotype
indicates where portion of shell was removed (and then replaced) in
course of preparation.]

[Illustration: PLATE 8

PLATE 8. _Gopherus flavomarginatus_ new species: Dorsal views of
paratypes (from top to bottom, IU 42953, IU 42954, and KU 39415),
approximately 1/5 natural size.]

[Illustration: FIG. 1. _Gopherus flavomarginatus_ new species: 1a and
1b--Lateral and ventral views of skull of holotype (x 1); 1c--Cross
section of paratype (USNM 60976) taken through middle of third central
lamina (x 2/5).]

_Anomalies._--There is a high incidence of anomaly in the type
series. Three of the specimens (USNM 60976, IU 42954, and KU 39415)
have a supernumerary central lamina. All of the specimens from
Durango are anomalous in regard to the marginal laminae. In the
holotype the first marginals are small, approximately as wide as
the small precentral. In the largest paratype (USNM 61254) the
first and second marginals are fused to form a single large scute
on each side. In the remaining Durangan paratype (USNM 60976) there
are eleven normal marginals on each side but a supernumerary lamina
occurs between the first and second marginal on the left and
between the precentral and first marginal on the right side. The
remaining three paratypes have the number of marginals that is
normal for the genus.

_Relationships._--_Gopherus flavomarginatus_ differs from all other
species of the genus by its larger size and by having an intergular
seam that is longer than the interhumeral seam. The possession of
a single, rectangular axillary scale, wider below than above,
also tends to distinguish _flavomarginatus_ from other living
_Gopherus_; in the other species this scute (frequently paired in
_berlandieri_) is generally triangular or at least pointed below.
Femoral spurs are developed to varying degrees in the other species
of _Gopherus_; they are usually lacking in individuals of small to
medium size. In large specimens of _agassizii_ and _polyphemus_