CACTACEA. 519 
180. Mamillaria pottsii, Scheer in Engelm. Synop. Cact. U.S. &c. p. 12. 
Texas.—Norta Mexico, Chihuahua, limestone rocks, 6000 to 7000 feet (Potts). 
181. Mamillaria prelii, Miiblenpf. in Otto & Dietr. Allg. Gartz. xiv. p. 372. 
Mexico. Hort. Kew. 
Salm Dyck (Cact. ed. 2, p. 116) regards this as a variety of MZ. viridis. 
182. Mamillaria pretiosa, Ehrb. in Otto & Dietr. Allg. Gartz. xvii. p. 200; 
“Walp. Ann. ii. p. 676. 
Mexico. 
183. Mamillaria (Anhalonium) prismatica, Lem. Hort. Univ. i. p. 231, t.1; 
Walp. Rep. ii. p. 309; Salm Dyck, Cact. ed. 2, p. 77. . 
Anhalonium retusum, Salm Dyck, Cact. 1844, p. 15. 
Ariocarpus retusus, Scheidw. Descr. Cact. Nonn. p. 2, t. 1. 
Mamillaria aloides, Monv. Cat. 1846, ex Labour. Cact. p. 153. 
Nortu Mexico, fissures of porphyritic rocks near San Luis de Potosi (Galeotti). 
184. Mamillaria procera, Ehrb. in Otto & Dietr. Allg. Gartz. 1849, p. 241. 
Mexico. Hort. Kew. 
185. Mamillaria pugionacantha, Forst. in Otto & Dietr. Allg. Gartz. xv. 
p. 50. 
MEXICO. 
186. Mamillaria pulchella, Hort. Berol., ex Salm Dyck, Cact. ed. 2, PP. 10 et 94. 
Mexico. Hort. Kew. 
Pfeiffer (Enum. p. 28) refers this to M. discolor. 
187. Mamillaria pulcherrima, Ehrb. in Otto & Dietr. Allg. Gartz. xvii. 
p. 242. 
Mexico. Hort. Kew. 
188. Mamillaria pulchra, Haw. in Bot. Reg. t. 1329. 
MEXICco. 
Pfeiffer refers this, with a doubt, to J. tentaculata. 
189. Mamillaria purpurea, Ehrb. in Otto & Dietr. "Allg Gartz. xvii. p. 270; 
Walp. Ann. ii. p. 677. 7 
MExIco. 
190.. Mamillaria pusilla, DC. Prodr. iii. p. 459, et Rev. t. 2. fig. 1. 
Cactus stellatus, Lodd. Bot. Cab. 1. t. 79. | 
Var. texana, Engelm. Cact. U.S. et Mex. Bound. Surv. p. 1.5, t. 5. 
Norra Mexico, common along the Rio Grande (Bigelow, Poseiger). 
The typical plant is from the West Inpies. Hort. Kew. 
