EXPLANATION OF THE LETTERING. 



a .Anus; bony axial rod supporting the cephalic appendages. 



ab .Abdomen. 



ab.a. . . Abdominal or branchial appendages. 



ab.cl .Ccelomic chambers of the abdomen. 



a.bm . Abductor branchial muscle. 



ab.t . . Abdominal temperature organs. 



a.c . .Anterior cornua; atrial or peribranchial chamber. 



a. card .Anterior cardinals. 



a.d Anterior dorsal plate. 



a.dl. Anterior dorso lateral plate. 



a. dp .Row of teeth on anterior margin of mandible. 



a.f Ant-orbital foramen. 



ag Argentea. 



a.h.co .Anterior haemal commissure. 



a.h.p .Anterior haemal process. 



a.l. Anal lobe. 



a.l.m .Alary muscle. 



a.m .Anterior marginal line of canal organs. 



an. .... .Anus. 



an.c. ... Anterior commissure. 



an.n.co .Anterior neural commissure. 



an.p .Anterior neuropore. 



an.pl Anal plate. 



a.n.s . Anterior neural spine. 



ao . . Aorta. 



ao.ar .Aortic arch. 



ap Apical plate; appendages. 



a.p .Anal plate. 



a. pi Apical plate. 



a.p.r Anterior bony entapophysis. 



a.s Anterior sclerotic plate. 



at Atrium; antennae. 



at.c. . . . .Atrial chamber; vestibule. 



at.d. . . .Excretory duct to antennal segment. 



at.r ... .Anterior triangular recess. 



au.o . .Auditory organ. 



a.v .Anterior median ventral. 



a. v.l .Anterior ventro-lateral plate. 



ba Basilar plate to the cephalic appendages 



b.c Blood cells. 



bd .Bud. 



bl Balancers. 



bl.c Blood corpuscles. 



b.nv Belly navel. 



b.o Branchial opening. 



473 



