EXPLANATION OF THE ILLUSTRATION 
Prare XXXIX. Variation in the cobs from Swallow 
Cave. A, Pre-Chapalote from Level 18; B, Early 
Chapalote from Level 2; C, Tripsacoid cob from 
Structures 1 and 2; D, Harinoso de Ocho from 
same; EK, Cristalino de Chihuahua from same; F, 
Long cob of Cristalino de Chihuahua from same, 
showing combination of long glumes and indura- 
tion. About two-thirds natural size. 
Inset. A, Karliest cob from Bat Cave, New Mexico. 
B, Earliest cob from Swallow Cave, Chihuahua, 
Mexico. Note the resemblance in shape between 
these two; C, Three views of kernels of modern 
Chapalote; D, Prehistoric kernels from Level 6, 
Dark Cave, Sonora, Mexico. Note similarities in 
size, shape and color, and in striations on dorsal 
surtace. Natural size. 
