_Comparisons._--From all other subspecies of _spinifer_, _T. s. emoryi_ can be distinguished by having a pale rim on the carapace that is four to five times wider posteriorly than it is laterally. This character, unique for _emoryi_, combined with patterns on the snout, side of head and carapace that are subject to little variation, permit ready identification of the subspecies _emoryi_. _T. s. emoryi_ resembles _pallidus_, and _guadalupensis_ and differs from _spinifer_, _hartwegi_ and _asper_ in having whitish tubercles or dots on the carapace. _T. s. emoryi_ resembles _guadalupensis_ but differs from _pallidus_, _spinifer_, _hartwegi_ and _asper_ in lacking conical tubercles along the anterior edge of the carapace on large females. For additional differences see accounts of other subspecies. Some populations of _T. s. emoryi_ resemble _T. muticus_ in the size at which sexual maturity is attained and in the development of the plastral callosities. _T. s. emoryi_ has a wide head that resembles that of _T. ferox_, _T. ater_, _T. s. asper_ and _T. s. guadalupensis_; _T. s. emoryi_ also resembles _T. ferox_ and _T. ater_ but differs from the other subspecies of _T. spinifer_ and _T. muticus_ in having a narrower carapace. _T. s. emoryi_ resembles _T. s. guadalupensis_, _T. s. pallidus_ and _T. ater_, and differs from the other subspecies of _spinifer_ and _T. muticus_, in having the carapace widest farther posteriorly than one-half way back on the carapace. _T. s. emoryi_ resembles _T. ferox_ in having the shortest length of snout of the subspecies of _spinifer_. The plastron is shorter than in _T. ferox_, longer than in _T. s. asper_, and about the same length as in _T. muticus_ and the other subspecies of _T. spinifer_. _Remarks._--Agassiz (1857, 1:407-08) did not designate a holotype in the original description of _Aspidonectes emoryi_; specimens are mentioned from the lower Río Grande of Texas, near Brownsville, and a stream of the Río Brazos drainage in Williamson County, Texas. The description is applicable to _T. s. emoryi_ as herein restricted, except for the statement that the white tubercles of young specimens are "encircled by faint black lines"; that statement is presumably based on the juveniles from Williamson County. _T. s. emoryi_ does not occur in Williamson County, Texas. Barbour and Loveridge (1929:225) listed MCZ 1909-10 and 1627 as cotypes. Stejneger (1944:65) mentioned MCZ 1909, 1913 and USNM 7855 as cotypes; the legend for Plate 20 (_op. cit._) refers to a drawing that "corresponds fairly closely with the type (MCZ 1910) collected at Brownsville, Texas, by Col. Emory."