344 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 PI. LXXVII. fig. 2. 



For the ventral longitudinal muscles see PL LXXVII. 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 ohliquus 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-tenjal ohliguus 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 ohliqims muscle (10) of the second segment of the mesosoma ; 

 the arthrodio-tergal ohliquus muscle (11) of the third segment of the mesosoma ; the 

 arthrodio-tergal ohliquus muscle (12) of the fourth segment of the mesosoma; the 

 arthrodio-tergal ohliquus muscle (13) of the fifth segment of the mesosoma; and the 

 arthrodio-tergal ohliquus muscle (14) of the sixth segment of the mesosoma, are all 

 similar in form and position to the arthrodio-tergal ohliquus 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 



