348 MISS E. J. BECK ON THE MUSCULAR 
They are united in a common attachment on the arthrodial membrane posterior to the 
segment. 
There are no muscles attached to the chitinous investment of the postanal spine or 
sting, though both 44 and 60 are attached to the arthrodial membrane connecting this 
body with the sixth metasomatic segment. 
Il. Dorso-Ventral Muscles. 
The dorso-ventral muscles of the Scorpion lie near the longitudinal median line; they 
are attached dorsally and ventrally to sclerites. Certain other muscles may be classed 
amongst the dorso-ventral muscles, which start from the tergites near the longitudinal 
median line and run ventrally, but before reaching the ventral surface have been inter- 
cepted by, and are attached to, the entochondrites. For the dorso-ventral muscles 
see Pl]. LX XVII. figs. 1, 4, 5, and Pl. LXXVIII. fig. 6. 
a. Prosoma. 
The dorso-chelicero-sternal muscle (61) is the most anterior of the dorso-ventral 
muscles. It is very small, and is attached to the carapace near the median line ante- 
rior to the central eyes; it runs forward ventrally, and is attached to the arthrodial 
membrane between the chelicere. 
The median dorso-preoral entosclerite muscle (62) is a large muscle, between which 
and its fellow of the opposite side are situated the eyes. It is attached dorsally to the 
carapace, and ventrally to the preoral entosclerite (besides the figures above cited, see 
Pl. LXXIX. fig. 12). 
The anterior dorso-plastron muscle (63) is attached dorsally to the carapace in the 
median line, being.joined to its fellow of the opposite side; they separate and are 
attached ventrally to the plastron. Through the arch thus formed pass the alimentary 
canal and the dorsal vessel (see Pl. LX XX. fig. 13). 
The median dorso-plastron muscle (64) is attached dorsally to the posterior portion 
of the carapace. It runs forward on the anterior surface of the posterior flap of the 
plastron to the body of the plastron, to which it is attached (Pl. LX XX. fig. 13). 
b. Mesosoma. 
The posterior dorso-plastron muscle (65) is attached to the tergite of the first segment 
of the mesosoma by the side of the pericardium. It runs forward, and at first lies 
closely on the posterior surface of the posterior flap of the plastron; it soon penetrates 
the flap, and continues its course on the anterior surface until it reaches the body of 
the plastron, to which it is attached. 
The dorso-suprapectinal-chondrite muscle (66) is attached to the second tergite of 
the mesosoma by the side of the pericardium. It runs forward to the suprapectinal 
chondrite, to which it is attached (see Pl. LXXIX. fig. 14). 
