The cusps shown in FIGS 3 and 4 are of course, {HEAD ~ cross sections} of {TAIL ~ modules} as exemplified in FIG 1, and can be extended indefinitely in a direction perpendicular to the section plane 
of
The cusps shown in FIGS 3 and 4 are of course , { HEAD ~ cross sections } of { TAIL ~ modules } as exemplified in FIG 1 , and can be extended indefinitely in a direction perpendicular to the section plane
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH