98 Journal New York Entomological Society, t^'^'- x>^ix, 



1916. RuEDEMANx. Median Eye in Trilobites. Proc. Nat. Acad. Sci., 2, 

 P- 234. 



1915. ScHUCHERT. Textbook of Geology. 



1892. Smith. Mouthparts of Copris with Notes on the Homologues of the 

 Mandibles. Trans. Amer. Ent. Soc., 19, p. 83. 



1 9 16. ToTHiLL. Ancestry of Insects. Amer. Jour. Sci., 42, p. 373. 



191 1. Walcott. Middle Cambrian Merostomata. Smithsonian Misc. Coll. 



57, No. 2, p. 19. 



191 2. Walcott. Middle Cambrian Banchiopoda, etc. Ibid., No. 6, p. 148. 

 1879. Wood-Mason. Morphological Notes Bearing on the Origin of Insects. 



Trans. Ent. Soc. London, 1879, p. 145. 



ABBREVIATIONS. 



a Basal condyle; "a" and "b" denote limits of points of attachment of 



mandible. 



b "a" and "b" denote extent of basal attachment of mandibular ap- 

 pendage. 



bg . . . .basignath, or basal region of mandible. 



c distal limits of basignath on outer surface of mandible. 



ci ....appendage called epicoxite in merostome gnathobase. 



d point at base of incisor process. 



dg . . . .distignath, or distal region of mandible. 



e apex of mandible. 



ei endites, or gnathobase (also called endognathite) ; ventral cirrus of 



annelid parapodium. 



en . . . .endopodite or inner branch of biramous limb; main axis of annelid 

 parapodium. 



ep .... epipodites or gills. 



ex . . . .exopodite or outer branch of biramous limb; dorsal cirrus of annelid 

 parapodium. 



/ molar process. 



g gnathofimbrium. 



gb ....gnathobase or endite of basal segment of limb. 



gf . . . .gnathofimbrium, or marginal fringe in distal region of mandible. 



li lacinia mobilis or epignath. 



in ....incisor process or incisor region ( incisorium ). 



Ini ....lacinia mobilis or epignath. 



nw . . . .molar process or mola. 



EXPLANATION OF PLATES VI, VII, VIII. 



Unless otherwise specified, all figures represent posterior views of right 

 mandibular appendage so oriented that apex is directed toward the top of the 

 page, and region normally bearing endopodite or palpus, is directed toward the 

 left-hand margin. 



