128 
The result of a closer inspection of the distribution of these nearly 
related forms is worthy of note. (. viviparus extends from British 
America and the Upper Missouri to eastern Colorado and western Kan- 
sas; neo-mexicanus (the form most nearly related to viviparus) extends 
from central Colorado and southern Utah into Mexico; at the south- 
eastern edge of this range begins radiosus and extends eastward 
through southern Texas; from the western edge of neo-mexicanus the 
form arizonicus extends westward into southern California, touching 
chloranthus at its Utah limit, and at its California extension reaching 
alversoni and deserti, the latter of which extends northward into the 
desert region of southeastern California and adjacent Nevada. Taking 
this type as of Mexican origin, it seems to have entered the United 
States from Sonora and Chihuahua, and to have spread in three direc- 
tions, viz.: eastward through southern Texas; westward and north- 
westward into southern California and southern Utah; and northward 
to the head waters of the Missouri and British America, though we 
would limit the northern extension of the present specific type to cen- 
tral Colorado, and would regard the still more northern forms as of the 
same origin but entitled to specific rank. 
2. ANHALONIUM Lem. Cact. Gen. Nov. (1839). 
Depressed or flattened, simple, unarmed plants, covered with peculiar 
imbricated tubercles above and their scale-like remains below: tubercle 
with lower aud upper parts very different; lower part comparatively 
thin and flat; upper exposed part triangular in outline and divergent, 
very thick and hard, the lower surface smooth and keeled, the upper 
surface plane or convex, smooth or tuberculate or variously fissured, 
with a broad wool-bearing groove or simply a more or less evident 
tomentulose apical areola: spine-bearing areole obsolete: flower-bearing 
areola at the summit of the lower pedunclelike portion of the very 
young tubercle (thus appearing axillary with reference to the exposed 
part of the tubercle) and bearing a dense penicellate tuft of long soft 
hairs which conceals the lower part of the flower and the entire fruit 
and persists about the apical region of the plant as matted and appar- 
ently axillary wool: ovary naked: seeds large, black, and tuberculate: 
embryo obovate, straight. 
According to the present views concerning generic limitations in Cactacew, Anha- 
lonium must certainly be kept distinct from Mamillaria, and to such a view Dr. 
Engelmann had finally come. The generic distinction is based upon such characters 
as (1) the complete suppression of the spine-bearing areol; (2) the strong differ- 
entiation of the tubercles into two very distinct regions; (3) the production of the 
flower at the apex of the basal or penduncle-like portion (which becomes flattened 
and expanded at maturity) of a very young tubercle; and (4) the large tuberculate 
seeds, 
In the case of engelmanni the broad woolly groove of the upper portion of the 
tubercle expands below into the flower-bearing areola, but terminates blindly above 
just behind the sharp apex. In prismaticum and furfuraceum the groove is obliter- 
ated, but there usually remains a small (more or less tufted) areola and depression 
