302 ARACHNIDA—SCORPIONIDEA CHAP. 
eyes of Limulus. The arrangement of various slight longi- 
tudinal ridges on the dorsal surface of the carapace is of systematic 
importance. On the ventral surface, just in front of the genital 
/) 
y IN 
y / Ni Aand 
_ Pedipalp 
Chelicera b Lateral eyes 
' _- Median eyes 
Syl Nig Provoma 
seed 7) Stee? 
aman NS 
if nomen AS XS, Mesosoma 
Metasoma 
aculeus. 
Fia. 169.—Buthus occitanus. A, Dorsal view; B, ventral view. (After Kraepelin. ) 
operculum, is a sternum, never large, and sometimes barely 
visible. Its shape and size constitute one of the principal 
family characteristics. 
Mesosoma.—The dorsal plates or terga are distinct, and are 
connected by soft chitin with their corresponding sterna. 
Beneath the second abdominal segments are borne the 
“pectines” or comb-lke organs. In their structure four 
portions are distinguishable, an anterior lamella or shaft attach- 
ing them to the body, a middle lamella, the teeth, and the 
fulera, a series of small chitinous pieces intercalated between the 
bases of the movable teeth. 
