OF THE AMERICAN KING-CRAB. 503 
Fig. 2. p. Anterior thoracetral vein. 
q. Middle thoracetral vein. 
r. Posterior thoracetral vein. 
s. Median thoracetral vein. 
u, u. Fasciculi of the * levatores telsoni.’ 
PLATE XXXVII. 
Limulus polyphemus. 
Fig. 1. Side view of heart, alimentary canal, and nervous system. 
À, 5, €, 1 & a 1, as in Pl. XXXVI. 
A'. Under or vaulted surface of cephaletron. 
B”. Anal segment of thoracetron. 
u. Antennula. 
11. Antenna. 
tv. Mandibula. 
v. Preemaxilla. 
vi. Maxilla. 
vit. Maxilliped. 
* Chilarion. 
vu. Lid-plate. 
1x. First gill-plate. 
x Second gill-plate. 
xr. Third gill-plate. 
xn. Fourth gill-plate. 
xu. Fifth gill-plate. 
b. Dorsal wall of cephaletron. 
c. Ventral wall of cephaletron. 
d. Digging-border of cephaletron. 
e. Holding-border of cephaletron. 
f. Cephaletral arch. 
g. Entering process of thoracetron. 
h. Entosternon. 
i. Intestine. 
m 1. Levatores thoracetri. 
m 7. Levatores telsoni. 
m 8. Obliqui telsoni. 
m 9. Depressores telsoni. 
n a. Ocellar nerve. 
n A. Ocular nerve. 
n 11. Antennular nerve. 
nir. Antennal nerve. 
niv. Mandibular nerve. 
nv. Preemaxillary nerve. 
n vi. Maxillary nerve. 
n vir. Maxillipedal nerve. 
