_Trionyx spinifer emoryi_, dorsal views. _Top_--Left, adult male, KU 51194 (× 2/7), Río Conchos, near Meoquí, Chihuahua, México; right, female, KU 3119 (× 4/9), Salt River, Phoenix, Maricopa County, Arizona. _Bottom_--Females; left, KU 3118 (× 1/5), locality same as KU 3119; right, TU 14453 (× 3/10), Pecos River, near junction with Independence Creek, Terrell County, Texas.] [Illustration: PLATE 45 _Trionyx muticus muticus_, juveniles, dorsal views. _Top_--Topotypes (× 1), Wabash River, 2 mi. S New Harmony, Posey County, Indiana; left, INHS 7278; right, INHS 7279. _Bottom_--Left, TU 14375 (× 3/4), Trinity River near junction with Big Creek, Liberty County, Texas; right, KU 50845 (× 1-2/5), 4 mi. N Atwood, Hughes County, Oklahoma.] [Illustration: PLATE 46 _Trionyx muticus muticus_, dorsal views. _Top_--Adult males; left, TU 14606 (× 3/10), White River, Cotter, Marion County, Arkansas; right, KU 48237 (× 1/3), 8 mi. S Hanover, Washington County, Kansas. _Bottom_--Females (× 1/4), 2 mi. E Manhattan, in Pottawatomie County, Kansas; left, KU 48229; right, KU 48238.] [Illustration: PLATE 47 _Trionyx muticus calvatus_, dorsal views. _Top_--Juvenile, TU 17303 (× 1-2/5), Pearl River, Varnado, Washington Parish, Louisiana. _Bottom_--Left, adult male, KU 47118 (× 3/10), Pearl River within 4 mi. of Monticello, Lawrence County, Mississippi; right, adult female, TU 17306 (× 2/9), Pearl River, 9 mi. S Monticello, Lawrence County, Mississippi.] [Illustration: PLATE 48 FIG. 1. Habitat of _T. s. pallidus_, Little River, 6.5 mi. S Broken Bow, McCurtain County, Oklahoma, September 7, 1953. FIG. 2. Habitat of _T. s. emoryi_, Río Mesquites, 2 mi. W Nadadores, Coahuila, México, July 27, 1959. Two _emoryi_ were trapped in hoop nets set in quiet water to left of what is believed to be a muskrat house.] [Illustration: PLATE 49 FIG. 1. General habitat of _T. s. pallidus_ and _T. m. muticus_, Lake Texoma, in a period of low water, 2 mi. E Willis, Marshall County, Oklahoma, February 24, 1951. FIG. 2. Type locality of _T. ater_, Tío Candido, 16 km. S Cuatro Ciénegas, Coahuila, México, July 30, 1959. An adult male of _T. s. emoryi_ was also netted here.] [Illustration: PLATE 50 FIG. 1. General habitat of _T. s. asper_ and _T. m. calvatus_, Escambia River, 2 mi. E, 1/2 mi. N Century, Escambia County, Florida, June 1, 1954. Three nests of _calvatus_ found on sand bar in foreground.]