No. I.] 



STUDIES ON LIMULUS. 



185 



EXPLANATION OF PLATES. 



REFERENCE LETTERS. 



In the colored plates nerves are represented in yellow, blood vessels in carmine, 

 cartilage in blue, and muscles in brick red. 



All exponential figures indicate the metamere to which the organ referred to 

 belongs. 



a.e.n. 

 a.i.n. 



a.tn.f. 



ao.a. 



a.v. 

 b. 



b.Tnem. 



b.t.mA and b 



car. 



d.l.p.e. 



dJ.p.t. 



e.b.m}-^^ 



endo. 



entaJ''^* 

 fb and 7 



f.ar. 

 f.br. 



h. 



anus. 



anterior commissure of 



brain, 

 anterior cornu of endo- 



cranium. 

 abdominal endochon- 



drites. 

 anterior ento-coxal nerve, 

 anterior intestinal branch, 

 alary muscles of heart, 

 anastomosing muscle 



fibers of heart, 

 aortic arch, 

 appendages, 

 abdominal spines upon 



edge of carapace, 

 anterior valve of heart, 

 base of muscle fiber of 



heart, 

 branchial cartilages, 

 branchio-cardiac canals, 

 basement membrane of 



heart, 

 branchio-thoracicmuscles. 

 collateral artery, 

 dorso-lateral plastro-enta- 



pophysial muscle, 

 dorso-lateral plastro- 



tergal muscle, 

 external branchial mus- 

 cles, 

 endocranium. 

 entocoxites. 

 entapophyses. 

 foramina of endocranium. 

 frontal artery, 

 fore-brain, 

 ganglion cells in median 



nerve of heart, 

 haemal branch of integu- 

 mentary nerve. 



h.d.3- and b 



h.ft.m.^'^* 

 hpr. 



ht. 

 i.b.ni. 



int. 



la. 

 La. 

 I. a.m. 



la.n. 



l.ar.^-'i 



I.e. 



l.c.n. 

 l.c.s. 



I.e. 



l.e.n. 



l.n. 



l.ol.n. 



l.p.pr. 



l.s.n. 



m. 



m.c.n. 



m.e. 



m.e.n. 



tnes. 



m.ey.n. 

 m.ti.'^^ 

 m.ol.n. 



hepatic ducts. 



haemal nerves. 



haemo-neural muscles. 



haemal processes of endo- 

 cranium. 



heart. 



internal branchial mus- 

 cle. 



inter-entapophysial mus- 

 cles. 



inter-tergal muscle (enta- 

 pophysial slip). 



intestinal nerves. 



intestine. 



labrum or rostrum. 



levator ani (muscle). 



longitudinal abdominal 

 muscles. 



labral, or rostral, nerves. 



lateral arteries. 



lateral cornua of endocra- 

 nium. 



lateral cardiac nerves. 



longitudinal connective- 

 tissue strands of heart. 



lateral eye. 



lateral eye nerve. 



lateral nerve. 



left olfactory nerve. 



latero-posterior process of 

 endocranium. 



lateral sympathetic nerve. 



mouth. 



median cardiac nerve. 



median eye. 



median ento-coxal nerve. 



meso-metasoma or abdo- 

 men. 



median eye nerve. 



mandibular nerves. 



median olfactory nerve. 



