LIMULUS AN ARACHNID. 613 
proctodzum or anal invagination, from which it is very 
sharply marked off by a groove and by the expansion and 
plication of the walls of the proctodeum. 
Alimentary canal. 4, of Scorpion (Buthus); 
after Newport. 2B, of Limulus. ps, 
pharyngeal sac; sal, salivary gland ; 
c! to c’, glandular ceca of the mid-gut, 
A M, Malpighian tube; pro, proctodseum. 
The corresponding section of the Scorpion’s alimentary 
tract also carries more than one pair of glandular ceca, and 
ends in a voluminous proctodzum, which commences, pre- 
cisely as in Limulus, in that region of the body which suc- 
VOL, XXI,—NEW SEK. SS 
