AND ENDOSKELETAL SYSTEMS OF SCORPIO. 355 
of the carapace. It runs inwards, and is attached to the posterior part of the first coxal 
entosclerite. 
The posterior first dorso-coxal entosclerite muscle (121) is attached posteriorly to the 
carapace. Running forwards, it is attached to the exterior edge of the first coxal 
entosclerite. 
The third dorso-coxal entosclerite muscle (122) is a thin broad muscle attached to 
the carapace towards its lateral portion and to the posterior margin of the posterior 
third coxal entosclerite. 
The fourth dorso-coxal entosclerite muscle (123) is attached to the carapace and to 
the posterior margin of the posterior fourth coxal entosclerite. 
Mesosoma.—To the first appendage of the mesosoma, or genital operculum, there is 
only one muscle, which is attached to the plastron, and has been already mentioned 
with the muscles which are attached to the plastron as the seventh plastron muscle 
(85). (See Pl. LXXX. figs. 13, 14.) 
To the second appendage, or pectine, there are six muscles, four of which are 
attached to the suprapectinal chondrite, and have been already mentioned with the 
muscles attached to the suprapectinal chondrite as the posterior (88), anterior (90), 
interior (91), and exterior (92) pectino-suprapectinal-chondrite muscles (see Pl. LX XIX. 
fig. 14). 
The epimero-pectinal muscle (124) is attached to the epimeron by the postero-lateral 
portion of the interior margin of the sixth coxal sclerite. It runs into the pectine 
(fig. 8). 
The sterno-pectinal muscle (125) is attached to the sternal sclerite, on which the 
pectines are carried near the median line; it runs laterally, and is attached to the 
interior portion of the opening of the pectine (Pl. LX XIX. fig. 14). 
No muscles are attached directly to the lung-books, although there are two series 
of muscles by which they are influenced. Amongst the ventral longitudinal muscles 
will be seen the post-stigmatic muscles (35, 36, 37, & 38) of the third, fourth, fifth, 
and sixth segments of the mesosoma; these are attached to the posterior edge of the 
stigmata and to the arthrodial membrane posterior to the segment in which they 
occur. 
The muscles of the other series run ventralwards from the pericardium, and spread 
out on the surface of the blood-holding lung-sac in those segments in which the lung- 
books occur. Of this series I shall speak later under the heading of “ Muscles to the 
Pericardium.” 
VII. Muscles to the Epimeron. (Plate LX XVII. fig. 1, and Plate LXX VIII. fig. 6 ) 
Muscles are distributed to the epimerou from the carapace, the plastron, the second 
entochondrite, and the pectines. All of these have been mentioned above, with the 
exception of those from the carapace. 
