AND ENDOSKELETAL SYSTEMS OF LIMULUS. 335 
Various plastro-entapophysial muscles are shown attached to the first ent- 
apophysis. One sees the inter-entapophysial muscles (4) passing from one 
entapophysis to the other, the tergo-pygals (6, 7, 8) and entapophysio-pygals 
(91, 92, 93), the external branchials (20), the small veno-pericardiacs (68) 
passing outwards and upwards across the intersternals. The larger vertical 
abdominals (12) also pass across the intersternals. Besides these the cut 
bases of the entapophyses are shown, and connecting these the inter-entapo- 
physial cartilages (ec); and at the sides of the anterior part of the figure are 
the lateral cornua of the plastron with their muscles 57, 58. 
On the left side of the figure the liver and genital organ have been 
removed, so as to expose the body of the entosternite or “ plastron” (P) and 
its dorsal process. ‘The dorsal entapophysio-plastra! (1) is now seen passing 
across the vertical muscles, and giving off various slips to the entapophyses. 
The pygal muscles and the cartilaginous band have been removed. 
Fig. 2. On the left side the dissection is more superficial than on the right: the course 
of the dorsal entapophysio-plastral muscle is more completely shown, the 
inter-entapophysials having been removed. ‘The anterior cornua of the plas- 
tron (A.c. en), with their muscles (49, 50, 51), are also seen; and posteriorly 
the sterno-pygals (10, 11) and entapophysio-pygals (88, 89, 90). ‘The abdo- 
minal sternites (s'—s*) lying on the floor of the mesosoma are also exposed. 
On the right side of the figure the above-named muscles have been removed, 
so as to show the course of the ventral entapophysio-plastral muscles (2 & 73) 
with their slips to the entapophyses. The entapophysio-metaplastrals have 
been cut, so as to show the posterior median process of the plastron (pcen). 
PLATE LXXIV. 
Fig. 1. All the overlying muscles have been removed, and thus the floor of the animal 
is exposed. On the right the distribution of the ventral longitudinal (3) 
and the intersternal muscles (5) is seen. ‘The slips passing from the various 
sternites to the entapophyses, and the vertical muscles (12) inserted in the 
abdominal sternites are also seen. 
On the left the aforenamed muscles have been removed in order to show 
the venous-collecting sinus (Vc) lying at the side of the floor of the animal, 
passing anteriorly above the plastron, where it has been cut. The veno- 
pericardiac muscles (68) are shown springing from this canal, and are turned 
towards the middle line. Passing up at the side of the canal are shown the 
hollow tendons of the branchio-thoracic muscles (18), each ending anteriorly 
in a muscular portion, which has been cut. Attached to the side of each 
abdominal entochondrite is seen a small muscle (48), the internal branchial. 
VoL. XI.—Pakt X. No, 4.—May, 1885. 35 
