Mamillaria sphaerica Dietr. Allg. Gart. Zeit xxi. 94 (1853).
Obovate or clavate, 5 cm. or more high, proliferous and at length
densely cespitose: tubercles elongated-ovate, acutish, 12 to 10
mm. long with axillary wool: radial spines 12 to 14, setaceous, 7
to 9 mm. long, bulbous at base, straight or curved, white;
central spine straight, subulate, somewhat shorter, but scarcely
stouter: flowers yellow, 3.5 to 5 cm. long: fruit unknown. Type
unknown.
Sandy ridges in the valley of the Rio Grande (both sides of the
river), from the mouth to Eagle Pass. Fl. from March throughout
the season.
Specimens examined: Texas (Schott of 1852): also specimens
cultivated in St. Louis in 1845 and 1861.
Dietrich's description was taken from plants collected by
Poselger at Corpus Christi. The Schott specimens are from Eagle
Pass. Dr. Engelmann calls attention to the fact that this
species approaches Coryphantha in its exserted ovary and large
flower, but the flowers are clearly from the growth of the
preceding season. The species is said to be too near the Mexican
C. longimamma of central and southern Mexico, but in the absence
of type specimens of either the question can not be settled. The
usual characterization of C. longimamma is as follows, which
seems to make it distinct enough: