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