ee 
iQ 
Fig 
MR. W. B. 8S. BENHAM ON THE MUSCULAR 
Outside the canal are seen the various branchial muscles rising from the 
mesosomatic appendages to their attachment in that portion of the entapo- 
physial ligament (ec) which partly embraces each entapophysis. 
. 2. A portion of the venous-collecting sinus, removed and enlarged ; in front the 
wall has been cut to show the apertures (O) of the descending vessels to the 
mesosomatic appendages. ‘The hollow portions of some of the branchio- 
thoracic muscles (18) are seen uniting to form the large muscular portion. 
Some of the branchial muscles are also seen. 
ig. 3. Two mesosomatic appendages seen from below. 
vu. The deep face of the anterior plate of the eighth appendage. The 
appendage is turned forwards. The posterior plate—except the portions 
which bear the gill-lamelle (/), and the “ stigmata” (s#g) leading into the 
hollow tendons of the branchio-thoracic muscles—has been dissected away. 
1x. is the inner face of the posterior plate of the ninth appendage, after 
removal of the anterior face. At the base of each appendage is an abdo- 
minal sternite (s) with muscles passing in various directions from it. The 
second pair of entapophyses (evt.2) are seen with a portion of the entapo- 
physial ligament (ec), to which some of the branchial muscles (21, 22, 23) 
are attached. Various sclerites (a.p.c) with their muscles (23, 48, 112, 113, 
114, 115) are also seen, which lie on the surface of the appendages. The 
tendons (ts) of the branchio-thoracic muscle are shown. 
_ 4. Inner surface of posterior plate of the seventh appendage, ‘“ genital operculum.” 
I P PP g 8 P 
The genital duct (gd) cut short is seen. 
ig. 5. Inner surface of anterior plate of the genital operculum. The stigmata (stg) 
of the basal portion (ts) of the branchio-thoracic muscle. The genital duct 
and aperture (gp), and the first pair of entapophyses are shown. 
PLATE LXXYV. 
Longitudinal sections. 
. 1, Shows two entocoxites (Hncx) with their muscles (25): the camerostome and 
basal part of first appendage and its muscle (24): the entosternite or 
plastron (P) and its muscles (49, 50, 51,52, 53): the course of the branchio- 
thoracic muscle (18) with its hollow tendons (fs) and their apertures (stg): 
the pygal muscles, attached partly to the tergum of the metasoma and partly 
to the hinder entapophyses (6, 7, 90, 91, 92). A few only of the branchial 
muscles (20, 22, 23) and two of the vertical mesosomatic muscles (12) are 
represented. This figure also shows the claw-like termination of the second 
appendage (11) characteristic of the male Limulus polyphemus. ‘The other 
prosomatic appendages have been cut short. 
