Crescent Milkvetch

Xylophacos aragalloides Rydb. Bull. Torrey Club 34: 48. 1907
Astragalus cyaneus S. Wats. Am. Nat. 9: 270, in part. 1875. Astragalus amphioxys A. Gray, Proc. Am. Acad. 13: 366, in part. 1878.
A perennial, with a cespitose caudex; stem about 1 dm. long, densely white-strigose; leaves 10-15 cm. long; stipules scarious, strigose, deltoid, 5-8 mm. long; leaflets 11-19, lanceolate or lance-elliptic, silky-canescent, 5-12 mm. long, 2-4 mm. wide; peduncles 5-10 cm. long; racemes 4-10-flowered; bracts lanceolate, 5-7 mm. long, attenuate; calyx strigose with black and white hairs, the tube 8 mm. long, the teeth subulate, 3-4 mm. long; corolla purplish, about 2 cm. long, similar to that of the preceding; pod lunate, tapering at each end, about, 4 cm. long, 7-8 mm. wide, deeply sulcate below, cross-reticulate, sparingly silky-strigose, curved about one third of a circle.
Type locality: St. George, Utah.
Distribution: Southwestern Utah and northern Arizona.

Xylophacos amphioxys (A. Gray) Rydb. Bull. Torrey Club 32:662. 1906.
Astragalus succumbens A. Gray, in J. C. Ives, Rep. Colorado Riv. Bot. 10. 1860. Not A. succumbens Dougl. 1831.
Astragalus Shortianus minor A. Gray, Proc. Am. Acad. 6: 211, in part. 1864.
Astragalus cyaneus S. Wats. Am. Nat. 9: 270. 1875. Not A. cyaneus A. Gray. 1849.
Astragalus Shortianus S. Wats.; Wats. & Rothr. Cat. PI. Wheeler's Surv. 7. 1874. Not A. Shortianus Nutt. 1838.
Astragalus amphioxys A. Gray, Proe. Am. Acad. 13: 366. 1878.
Astragalus crescenticarpus Sheldon. Minn. Bot. Stud. 1: 148. 1894.
Astragalus selenaeus Greene, Erythea 3: 76. 1895.
A perennial or biennial, with a deep root; stems several from the base, about 1 dm. high, silvery-canescent ; leaves ascending, 5-10 cm. long; stipules deltoid, scarious, 3-5 mm. long, canescent; leaflets 1 1—17, obovate, silky-canescent with hairs tapering at each end, 6—12 mm. long, 4-6 mm. wide, mostly obtuse at the apex; peduncles 5-10 cm. long; racemes 4—12flowered, 2-6 cm. long; bracts lanceolate, 2-4 mm. long; calyx silky-canescent, the tube 8 mm. long, the teeth subulate, 3 mm. long; corolla purple, moderately arched at the middle, with a pale spot; blades of the wings oblanceolate, slightly lunate, obtuse, about as long as the claws; keel-petals broadly lunate, rounded at the apex; pod narrowly lunate, tapering at each end, arched nearly into a semicircle, 3-4 cm. long, 6-7 mm. wide, and 4—5 mm. thick, somewhat sulcate on the lower suture, cross-reticulate, silky-strigose.
Type locality: Dona Ana, New Mexico.
Distribution: Texas to southern Utah, Arizona, and northern Chihuahua.

Xylophacos melanocalyx Rydb. Bull. Torrey Club 52: 149. 1925.
Astragalus amphioxys M. E. Jones, Rev. Astrag. 214, in part. 1923. Astragalus amphioxys X Layneae M. E. Jones, Rev. Astrag. 215. 1923.
A perennial, with a cespitose calyx; stems many, 2-7 cm. long, decumbent or ascending, white-strigose, densely covered with leaves; leaves 5-10 cm. long, ascending or spreading; stipules deltoid, 5-8 mm. long, white-strigose; leaflets 11-19, oval or obovate, 5-10 mm. long, 2-5 mm. wide, white silky-strigose on both sides, obtuse at each end; peduncles 7-15 cm. long, erect, white-strigose; bracts lanceolate, 2-3 mm. long, membranous; flowers subsessile; calyx black-hairy, the tube 6-7 mm. long, 3-3.5 mm. broad, the lobes deltoid-subulate, 2 mm. long; corolla bluish-purple, 15-18 mm. long; banner obovate, moderately arched; wings shorter, the blade oblong, acutish, with a large reflexed basal auricle; keel-petals nearly as long as the keel, the blades lunate, rounded at the apex ; pod crescent-shaped, about 3 cm. long, 1 cm. thick, and 5-7 mm. wide, crosswrinkled , white-strigose with somewhat kinked hairs.
Type locality: Copper Mine (west of St. George), Utah. Distribution: Northwestern Arizona and southwestern Utah.