THELOCACTUS. 9 
Densely cespitose, short-cylindric, 10 to 15 cm. long; ribs 8 to 13, sometimes spiraled, obtuse, 
tubercled; radial spines 7 to 20, at first light yellow, in age gray, spreading or recurved, unequal, 
the longer ones 4 cm. long, more or less annulate; central spine solitary, at first blackish, but in age 
gray, up to 5 cm. long; flowers yellow, 5 cm. long; inner perianth-segments numerous, lanceolate, 
acute; ovary and flower-tube bearing broad imbricated scales. 
T ype locality: Near Zimapan, Mexico. 
Dist-ibution: Zimapan and Ixmiquilpan, Mexico. 
We are inclined to refer here Echinocactus ehrenbergii Pfeiffer (Allg. Gartenz. 6: 275. 
1838), which, according to Schumann, also came from Ixmiquilpan, Mexico. In his mono- 
graph Schumann describes the flowers as yellow like those of /. leucacanthus, but in his 
English Keys he says that the flowers are rose-red. Dr. Rose, who collected in this region 
in 1905, found only one species of this relationship. 
Fic. 6.—Thelocactus buekii. Fic. 7.—Thelocactus leucacanthus. 
Echinocactus tuberosus Salm-Dyck (Forster, Handb. Cact. 287. 1846) is known only as 
a synonym. 
Echinocactus tuberosus subporrectus (Forster, Handb. Cact. 523. 1846) belongs here. 
Illustrations: Pfeiffer and Otto, Abbild. Beschr. Cact. 1: pl. 14; Abh. Bayer. Akad. 
Wiss. Miinchen 2: pl. 2, f. 10; pl. 3, f. 4, as Echinocactus leucacanthus. 
Figure 7 is from a photograph of the plant collected by Dr. Rose at Ixmiquilpan in 
1905. 
7. Thelocactus nidulans (Quehl). 
Echinocactus nidulans Quehl, Monatsschr. Kakteenk. 21: 119. 1911. 
Simple, depressed-globose, 10 cm. high, sometimes 20 cm. in diameter, gray, usually glaucous; 
ribs 20 to 25, rather indistinct, divided into tubercles; spines about 15, all similar, 2 to 6 em. long; 
flowers 4 cm. long, yellowish white. 
Type locality: Mexico. 
Distribution: Mexico, but known only from cultivated plants. 
Illustrations: Monatsschr. Kakteenk. 22: 51; Alianza Cientifica Universal 3: 114, as 
Echinocactus nidulans. 
Figure 8 is from a photograph given to Dr. Rose by Frantz de Laet in 1912. 
