AND ENDOSKELETAL SYSTEMS OF SCORPIO. 345 
posterior end to the lateral portion of the arthrodial membrane at the posterior angle 
of the segment. It bends round to the tergite, to which it is attached. 
The Jatero-dorsal muscle (16) of the second segment of the mesosoma; the latero- 
dorsal muscle (17) of the third segment of the mesosoma; the datero-dorsal muscle (18) 
of the fourth segment of the mesosoma; the /atero-dorsal muscle (19) of the fifth segment 
of the mesosoma ; and the Jatero-dorsal muscle (20) of the sixth segment of the meso- 
soma, are all similar in form and position to the latero-dorsal muscle (15) of the first 
segment of the mesosoma. 
Ventral.—The median antero-posterior muscle (21) of the third segment of the 
mesosoma runs along the median line from the arthrodial membrane anterior to the 
sternite, to the arthrodial membrane posterior to the sternite. As this muscle is in the 
median line it is not repeated on each side of the animal (Pl. LX XVII. fig. 3). 
The median antero-posterior muscle (22) of the fourth segment of the mesosoma; the 
median antero-posterior muscle (23) of the fifth segment of the mesosoma; and the 
median antero-posterior muscle (24) of the sixth segment of the mesosoma, are similar 
to the median antero-posterior muscle (21) of the third segment of the mesosoma. 
The lateral antero-posterior muscle (25) of the first segment of the mesosoma is 
attached anteriorly to the plastron, and posteriorly to the suprapectinal chondrite 
(Pl. LXXX. fig. 14). 
The lateral antero-posterior muscle (26) of the second segment of the mesosoma is 
attached anteriorly to the suprapectinal chondrite, and posteriorly to the sternite of 
the third segment (Pl. LX XVII. fig. 5, and Pl. LX XIX. fig. 14). 
The lateral antero-posterior muscle (27) of the third segment of the mesosoma is a 
similar muscle to (26), but is attached anteriorly to the sternite of its own segment, 
and posteriorly to the sternite of the following segment. This muscle is lateral to the 
median antero-posterior muscle (21) of the first segment of the mesosoma. 
The lateral antero-posterior muscle (28) of the fourth segment of the mesosoma, and’ 
the lateral antero-posterior muscle (29) of the fifth segment of the mesosoma are 
similar to the lateral antero-posterior muscle (27) of the third segment of the meso- 
soma, and are attached anteriorly to the sternite of the segment to which they belong 
and posteriorly to the sternite of the following segment. 
The lateral antero-posterior muscle (30) of the sixth segment of the mesosoma is 
similar to the lateral antero-posterior muscle (27) of the third segment of the meso- 
soma, except that it is attached anteriorly to the sternite of the sixth segment, and 
posteriorly to the arthrodial membrane posterior to the segment. 
The arthrodio-sternal obliquus muscle (31) of the third segment of the mesosoma is 
a small muscle superficial to the lateral antero-posterior muscle (27), attached poste- 
riorly to the arthrodial membrane posterior to the segment. It runs obliquely forward 
towards the median line, and is attached anteriorly to the sternite. 
The arthrodio-sternal obliquus muscle (32) of the fourth segment of the mesosoma, 
3 F2 
