The North American Species of [23]
by boiling, before the presence or absence of the groove can be definitely determined. The species and varieties are indicated only by their specific or varietal names in the following key, and the numbers refer to the serial numbers of the synoptical presentation. Forms occurring within the United States are marked with an "*":
I. Tubercles never grooved.
* Central spines none.
Radials 5 to 9, stout. meiacanthus* (7).
Radials 20 to 40. micromeris* (12), greggii (13).
Radials 40 to 80. lasiacanthus* (10), denudatus* (11).
** Central spine solitary and not hooked.
+ Central spine longer than the radials.
Radials 7 or 8: tubercles very long (40 to 50 mm.). longimamma (36).
Radials 15 to 20: tubercles 6 to 8 mm. long. eschanzieri (21).
++ Central spine shorter than the radials.
Radials 5 to 9, stout. meiacanthus* (7).
Radials 9 to 22. heyderi* (5), hemisphaericus* (6), gummiferus (8), gabbii (34), sphaericus (35).
*** Central spine solitary and hooked.
+ Stems slender cylindric: Lower Californian.
Centrals 1, 20 to 30 mm. long. roseanus (23).
Centrals 1 to 4, 20 to 50 mm. long. setispinus (24).
++ Stems depressed-globose to ovate.
Radials 4 to 6, rigid. uncinatus (9).
Radials 8 to 12. wrightii* (15).
Radials 15 to 30. grahami* (19), eschanzieri (21).
Radials 50 to 60. barbatus (18).
**** Central spines more than one, and none of them hooked.
+ Slender or sometimes stout cylindrical plants, branching at base: Lower Californian.
brandegei (3), setispinus (24), halei (25).
++ Depressed-globose to ovate and stout cylindrical.
++ Radials few (3 to 12) and rigid: Mexican.
Radials 3: centrals 3. alternatus (1)
Radials 7 or 8: tubercles 40 to 50 mm. long. longimamma (36).
Radials 10 to 12: tubercles 12 to 15 mm. long. gummiferus (8). ++++ Radials numerous (16 to 60), capillary or bristle-like.
Radials 15 to 30, slender but rigid (bristly). acanthophlegmus(2), densispinus (4), bispinus (14), rhodanthus (26), sulphureospinus (27), palmeri (29), pringlei (32).
Radials 30 to 60 or more, mostly capillary. tetrancistrus* (22), capillaris (28), texanus* (31), spaerotrichus (33).
***** Central spines more than one and but one of them hooked.
Radials 10 to 15. goodrichii* (16), setispinus (24).
Radials 15 to 30. pondii (17), grahami* (19), bocasanus (20).
Radials 30 to 60. tetrancistrus (22).
****** Central spines more than one, and more then one of them hooked.
Radials 8 to 12. wrightii* (15).
Radials 30 to 60. tetrancistrus (22).
II. Tubercles with a more or less prominent groove.
* Central spines none.
+ Radials whitish and rigid, oppressed (pectinate) and interwoven with adjacent clusters.
Depressed-globose and simple. compactus (44).
Globose and simple. radians* (45), corniferus (47).
Cespitose. pectenoides (46), sulcatus* (49).
++ Radials more slender and spreading.
Radials 10 to 17. missouriensis* (37), similis* (38), macromeris* (64).
Radials 30 to 50, capillary. dasyacanthus* (51).
** Central spine solitary, not hooked.
+ Central spine porrect.
Radials 6 to 17. missouriensis* (37), robustior* (39), scheerii* (40).
Radials 30 to 50, white and capillary. dasyacanthus* (51).
++ Central spine curved downwards.
Radials 8 to 12. sulcatus* (49).
Radials 12 to 26. robustispinus (41), recurvatus (42), corniferus (47), scolymoides* (48).
+++ Central spine erect: Mexican.
Radials 7 or 8: central 50 mm. long. salm-dyckianus (43).
Radials 10 or 11: central 25 to 35 mm. long. maculatus (52).
Radials 13 to 16. compactus (44).
*** Central
I. Tubercles never grooved.
* Central spines none.
Radials 5 to 9, stout. meiacanthus* (7).
Radials 20 to 40. micromeris* (12), greggii (13).
Radials 40 to 80. lasiacanthus* (10), denudatus* (11).
** Central spine solitary and not hooked.
+ Central spine longer than the radials.
Radials 7 or 8: tubercles very long (40 to 50 mm.). longimamma (36).
Radials 15 to 20: tubercles 6 to 8 mm. long. eschanzieri (21).
++ Central spine shorter than the radials.
Radials 5 to 9, stout. meiacanthus* (7).
Radials 9 to 22. heyderi* (5), hemisphaericus* (6), gummiferus (8), gabbii (34), sphaericus (35).
*** Central spine solitary and hooked.
+ Stems slender cylindric: Lower Californian.
Centrals 1, 20 to 30 mm. long. roseanus (23).
Centrals 1 to 4, 20 to 50 mm. long. setispinus (24).
++ Stems depressed-globose to ovate.
Radials 4 to 6, rigid. uncinatus (9).
Radials 8 to 12. wrightii* (15).
Radials 15 to 30. grahami* (19), eschanzieri (21).
Radials 50 to 60. barbatus (18).
**** Central spines more than one, and none of them hooked.
+ Slender or sometimes stout cylindrical plants, branching at base: Lower Californian.
brandegei (3), setispinus (24), halei (25).
++ Depressed-globose to ovate and stout cylindrical.
++ Radials few (3 to 12) and rigid: Mexican.
Radials 3: centrals 3. alternatus (1)
Radials 7 or 8: tubercles 40 to 50 mm. long. longimamma (36).
Radials 10 to 12: tubercles 12 to 15 mm. long. gummiferus (8). ++++ Radials numerous (16 to 60), capillary or bristle-like.
Radials 15 to 30, slender but rigid (bristly). acanthophlegmus(2), densispinus (4), bispinus (14), rhodanthus (26), sulphureospinus (27), palmeri (29), pringlei (32).
Radials 30 to 60 or more, mostly capillary. tetrancistrus* (22), capillaris (28), texanus* (31), spaerotrichus (33).
***** Central spines more than one and but one of them hooked.
Radials 10 to 15. goodrichii* (16), setispinus (24).
Radials 15 to 30. pondii (17), grahami* (19), bocasanus (20).
Radials 30 to 60. tetrancistrus (22).
****** Central spines more than one, and more then one of them hooked.
Radials 8 to 12. wrightii* (15).
Radials 30 to 60. tetrancistrus (22).
II. Tubercles with a more or less prominent groove.
* Central spines none.
+ Radials whitish and rigid, oppressed (pectinate) and interwoven with adjacent clusters.
Depressed-globose and simple. compactus (44).
Globose and simple. radians* (45), corniferus (47).
Cespitose. pectenoides (46), sulcatus* (49).
++ Radials more slender and spreading.
Radials 10 to 17. missouriensis* (37), similis* (38), macromeris* (64).
Radials 30 to 50, capillary. dasyacanthus* (51).
** Central spine solitary, not hooked.
+ Central spine porrect.
Radials 6 to 17. missouriensis* (37), robustior* (39), scheerii* (40).
Radials 30 to 50, white and capillary. dasyacanthus* (51).
++ Central spine curved downwards.
Radials 8 to 12. sulcatus* (49).
Radials 12 to 26. robustispinus (41), recurvatus (42), corniferus (47), scolymoides* (48).
+++ Central spine erect: Mexican.
Radials 7 or 8: central 50 mm. long. salm-dyckianus (43).
Radials 10 or 11: central 25 to 35 mm. long. maculatus (52).
Radials 13 to 16. compactus (44).
*** Central