544 MISS E. J. BECK ON THE MUSCULAR 
one set of longitudinal muscles, which is situated in the posterior portion, and moves 
the carapace on the first segment of the mesosoma. 
For the dorsal longitudinal muscles see Pl. LXXVII. fig. 2. 
For the ventral longitudinal muscles see Pl. LX XVII. fig. 3. 
a. Prosoma. 
Dorsal.—The antero-posterior muscle (1) is a large muscle running parallel with the 
longitudinal median line. It extends laterally from the pericardium to the side of the 
animal. Anteriorly it is attached to the carapace, and posteriorly to the arthrodial 
membrane posterior to the carapace. 
The arthrodio-tergal obliquus muscle (2) is smaller, and is attached posteriorly to 
the arthrodial membrane between the carapace and the first segment of the mesosoma. 
It is superficial to the antero-posterior muscle (1), and runs obliquely forward towards 
the median line, being attached anteriorly to the carapace. 
Ventral.—There are no ventral longitudinal muscles in the prosoma. 
b. Mesosoma. 
Dorsal.—The antero-posterior muscle (3) of the first segment of the mesosoma runs 
parallel with the median line, stretching laterally from the pericardium to the side of 
the body. It is attached anteriorly and posteriorly to the arthrodial membrane, ante- 
rior and posterior to the segment. 
The antero-posterior muscle (4) of the second segment of the mesosoma; the antero- 
posterior muscle (5) of the third segment of the mesosoma ; the antero-posterior muscle 
(6) of the fourth segment of the mesosoma; the antero-posterior muscle (7) of the fifth 
segment of the mesosoma; and the antero-posterior muscle (8) of the sixth segment of 
the mesosoma, are exactly similar to the antero-posterior muscle (3) of the first segment 
of the mesosoma. 
The arthrodio-tergal obliquus muscle (9) of the first segment of the mesosoma is 
attached posteriorly to the arthrodial membrane between the first and second segments. 
It is superficial to the antero-posterior muscle (3), and runs obliquely forward towards 
the median line, being attached anteriorly to the tergite. 
The arthrodio-tergal obliquus muscle (10) of the second segment of the mesosoma ; 
the arthrodio-tergal obliquus muscle (11) of the third segment of the mesosoma; the 
arthrodio-tergal obliquus muscle (12) of the fourth segment of the mesosoma; the 
arthrodio-tergal obliquus muscle (13) of the fifth segment of the mesosoma; and the 
arthrodio-tergal obliquus muscle (14) of the sixth segment of the mesosoma, are all 
similar in form and position to the arthrodio-tergal obliquus muscle (9) of the first 
segment of the mesosoma. 
The latero-dorsal muscle (15) of the first segment of the mesosoma is attached at its 
