The two juvenal syntypes (5.2 and 6.1 cm. in plastral length) from Williamson County, Texas, are both catalogued as MCZ 1627, but only one of these bears a catalogue number. The two softshells are not emoryi, and are more nearly like T. s. guadalupensis than T. s. pallidus. Actually, they are from an area of intergradation between those subspecies (see comments concerning intergradation under the accounts of the subspecies pallidus and guadalupensis). White spots occur on the carapaces anteriorly and posteriorly, the larger (more posterior) of which are encircled with dusky ocelli. The carapace of the small specimen (bearing no number) is brown having a few, small black specks intermixed with the white spots. The carapace of the large specimen is pale lavender and has a more obscure pattern than the other specimen.
After Agassiz's description, emoryi was accepted as a distinct species. Neill (1951:15) suggested that emoryi was subspecifically related to T. ferox. Crenshaw and Hopkins (1955) and Schwartz (1956), however, demonstrated that ferox was a distinct species; emoryi has since been considered a subspecies of T. spinifer.
Two specimens having blackish dots on the carapace, indicate relationship with T. s. guadalupensis. USNM 7638, a hatchling, has large whitish dots surrounded by blackish dots confined to the posterior half of the carapace, and the locality for this specimen is merely Río Bravo (= Río Grande). CNHM 47366, a hatchling from Sierra de las Palmas (Sierra de Santa Rosa, La Palma), Coahuila, has a few, small, blackish dots, irregularly spaced, on the anterior half of the carapace, but other dots more evenly distributed on the posterior half where they are intermixed with whitish dots. The drawing of the dorsal view of a hatchling emoryi (Agassiz, 1857:Pl. 6, Fig. 4) shows a sprinkling of blackish dots on the anterior half of the carapace. A hatchling from Eagle Pass (USNM 116578) does not have a noticeably widened pale rim posteriorly on the carapace, and is not distinguishable from pallidus. See account of T. s. guadalupensis for further comments on intergradation.
A soft-shelled turtle that was obtained in the Sacramento River by three fishermen, near Sacramento, California, was named Aspidonectes californiana by Rivers (1889:233). A comparison (with Aspidonectes spinifer and A. emoryi) of certain features of the skull was largely prepared by Baur and included in the description (op. cit.:234-35); seemingly, the most trenchant character of the skull of californiana was the enlarged alveolar surfaces of the jaws. This feature prompted Baur (1893:220) to refer californiana to the genus Pelodiscus, which also included agassizi (skulls also having jaws with enlarged alveolar surfaces) and several Old World species. Van Denburgh (1917) discussed the origin of the specimen that formed the basis of River's description and concluded that it was brought over from China. Siebenrock (1924:192) and Mertens and Wermuth (1955:389) listed Aspidonectes californiana as a synonym of emoryi. River's description is not that of emoryi; the enlarged alveolar surfaces of the jaws, and the dark carapace having tubercular ridges suggest a resemblance to T. ferox. The papillae on the neck are not found in any American species. Miller (1946:46, footnote 2) believed that "it obviously was introduced, apparently from China," and cited Pope (1935:61), who declared the specimen to represent Trionyx sinensis.
Schmidt (1924:64) first reported the occurrence of T. s. emoryi west of the continental divide in Arizona and suggested that it was highly probable that the species had been introduced near Phoenix in recent years. Cowles and Bogert (1936:42) mentioned a species of softshell occurring in the Boulder Dam region and presumed the species to be native to Asia and introduced by the Chinese. Linsdale and Gressitt (1937:222) determined the status of the species in the Colorado River drainage as T. s. emoryi. The discussions by Dill (1944:179-81) and Miller (1946:46) indicate that emoryi was introduced into the Gila River (Colorado River drainage) in western New Mexico near the turn of the century.
T. s. emoryi and T. ater are the only kinds of softshells occurring in México. The colloquial name for soft-shelled turtles in México is "tortuga blanca." This name is also used in reference to the Central American river turtle, Dermatemys mawei, which occurs on the east coast of México as far north as Veracruz.
Specimens examined.—Total 275, as follows: Arizona: Maricopa: CNHM 4768, KU 2214-19, 2803, 2824, 2837, 2903-07, 2909-16 (2914, 2 specimens), 2918-29, 3118-27, 3129, 3147-56, USNM 71627, Salt River, Phoenix. Pinal: UI 37713, Gila River, 6 mi. E Winkleman; UMMZ 92006-07, Gila River, 1/2 mi. [516] below Coolidge Dam; UMMZ 105824, San Pedro River about 1 mi. above confluence with Gila River.
Nevada: Clark: AMNH 58370, Boulder City boat landing, Lake Mead; TU 15802, Virgin River, Mesquite.
New Mexico: Eddy: KU 15938, Carlsbad; KU 48217-18, Black River Village. Grant: AMNH 79911, Gila River, 8 mi. NE Cliff.