350 MISS E. J. BECK ON THE MUSCULAR 
the plastron on the anterior side of the base of the anterior process. It runs forward, 
and is attached anteriorly to the second coxal sclerite. 
The posterior second coxo-plastron muscle (76) is attached posteriorly to the body of 
the plastron posterior to the attachment of the muscle 75. It runs forward, and is 
attached to the second coxal sclerite. 
The fourth deutomerite-plastron muscle (77) is attached to the lateral portion of the 
body of the plastron posterior to the anterior process. It runs into the fourth appen- 
dage, and is attached to the interior margin of the deutomerite sclerite. 
The fourth postcoxal entosclerite plastron muscle (78) is attached to the median 
lateral process of the plastron. It spreads out on the posterior surface of the fourth 
coxal entosclerite, to which it is attached. 
The anterior epimero-plastron muscle (79) is attached to the lateral portion of the 
body of the plastron posterior to the median lateral process, and to the arthrodial 
membrane between the fourth and fifth appendages behind the posterior fourth coxal 
entosclerite. 
The fifth deutomerite-plastron muscle (80) is attached to the posterior process of the 
plastron, running into the fifth appendage. It is attached to the interior margin of the 
deutomerite sclerite. 
The median epimero-plastron muscle (81) is attached to the posterior process of the 
plastron and to the lateral portion of the arthrodial membrane between the fifth and 
sixth appendages. 
The stath deutomerite-plastron muscle (82) is attached to the posterior process of the 
plastron. It runs into the sixth appendage, and is attached to the interior margin of 
the deutomerite sclerite. 
The posterior epimero-plastron muscle (83) is attached to the posterior part of the 
body of the plastron. It runs laterally for a short distance on the anterior surface of 
the posterior flap of the plastron, but soon penetrates the flap, and continues on 
the posterior surface (see Pl. LX XX. figs. 13 & 14). It is attached to the arthrodial 
membrane posterior to the sixth coxal sclerite. 
The sterno-subneural plastron muscle (84) is a small muscle attached to the anterior 
subneural process of the plastron, and, ventrally, to the small postoral entosclerite. 
The operculo-plastron muscle (85) is attached to the posterior part of the subneural 
portion of the plastron and to the seventh appendage or genital operculum. 
The plastron-suprapectinal-chondrite muscle (86) is a small muscle attached ante- 
riorly to the posterior part of the subneural portion of the plastron, and posteriorly to 
the anterior face of the suprapectinal chondrite. 
The lateral antero-posterior muscle (25) has already been mentioned with the ventral 
longitudinal muscles. It starts from the posterior part of the subneural portion of 
the plastron, and is attached posteriorly to the suprapectinal chondrite. 
The sixth coxo-plastron muscle (86 a) is attached to the lateral portion of the plastron 
