9(] MUSCULAR SYSTEM. 



PI. LX. — 9 lies immediately outside No. 4, but is 

 somewliat straigliter, as it is not affected by No. 5. 



PI. LIX. — 10 rises nearly in the centre of tbe side- 

 wall, opposite the middle part of No. 6, and, passing 

 backwards, is attached close to the posterior end of 

 No. 4. 



PL LX. — 11 lies just outside No. 10, and has the 

 same direction and attachments. In some specimens 

 these two muscles seemed to form one only. 



PI. LX. — 12. This j)owerful muscle is the principal 

 extensor of the tail, and passes forwards along the 

 ventral surface, through the antepenultimate segment, 

 and is attached at the anterior end of the third abdo- 

 minal segment. 



These are the principal muscles of the fourth ab- 

 dominal segment ; I will now proceed to describe 

 those of the third. 



1. This muscle corresponds to the muscle No. 1, of 

 the fourth segment, immediately in front of which it 

 lies, and with which, in some specimens, as already 

 mentioned, it even forms one continuous muscle. It 

 generally, however, commences near the middle line of 

 the back, on the side of the dorsal vessel, and directly 

 in front of the anterior end of the corresponding 

 muscle of the following segment, and, passing straight 

 forwards, is attached to the anterior margin of the 

 segment. 



PI. LX. — 2. This muscle, as in the fourth segment, 

 is smaller than, and lies under, or rather outside of, 

 the preceding. 



Pis. LIX and LX. — 3 rises at the anterior end of 

 the segment, partly under, and partly at the side of 

 No. 1, and passes rather diagonally backwards under 

 No. 2. 



Pis. LIX and LX. — 4 runs at the side of, and 

 parallel to. No. 3. 



PI. LIX. — 5 rises at the side of No. 1, and passes 

 forward parallel to it, but, instead of being attached at 

 the anterior end of the segment, passes forward, 



