328 ME. W. B. S. BENHAM ON THE MUSCULAR 



No. 40. This muscle passes beneath 39, and goes to the fourth entocoxite (corre- 

 sponds to 34). 



No. 41. This muscle is similar to 32, 35, and 38, and goes to the fifth prosomatic 

 appendage: s, its anterior; t, posterior branch. 



No. 42. This muscle lies parallel to but behind 39, and passes backwards to the fifth 

 appendage (corresponds to 33, 36, and 39). 



No. 43. This muscle rises under and behind 40, passes beneath 42, and goes to fifth 

 limb. It corresponds to 34, 37, and 40. 



No. 44. This muscle is similar to 32, 35, 38, and 41, and goes to sixth appendage: y, 

 its anterior, z, its posterior branch. It rises from the postero-lateral process of the ento- 

 chondrite. 



No. 45. Rises behind 42, runs parallel to it, and goes to the sixth appendage, passing 

 under 44. 



No. 46. This is a much larger muscle than the corresponding ones 34, 37, 40, 43, 

 rising from the middle line of the ventral surface of the body of the prosomatic ento- 

 chondrite, beneath and behind the previous muscles of the limbs, and, passing rather 

 backwards, goes to the sixth appendage. 



No. 47. Is smaller than 46, rises behind it, and goes outwards to the entocoxite of 

 the sixth appendage. 



No. 60. Rises from the postero-lateral process of the plastron behind 44, and goes to 

 the posterior border of the entocoxite. 



b. Mesosomatic Appendages. — The muscles connected with these have nearly all been 

 described under the heading " Dorso-ventral Muscles." These are: — 



No. 20. The external branchials : six pairs. 



No. 21. The anterior entapophysio-branchials: six pairs. 



No. 22. The posterior entapophysio-branchials. 



No. 23. The pre-entapophysio-branchials: five pairs. 



No. 48. The Internal Branchial Muscles. — Rising from the ventral ridge of the first 

 mesosomatic entochondrite a small muscle dips into the genital operculum, and is 

 distributed partly to its anterior and partly to its posterior lamella (see PI. LXXIV. 

 figs. 4 & 5). 



A similar muscle occurs in the five succeeding appendages (PI. LXXIV. fig. 3). 



No. 18. The Branchio-thoracic Muscles have been described above ; they rise from 

 the tendinous portion of the stigmata, which lie at the base of the posterior lamella of 

 each of the six pairs of mesosomatic appendages, near the middle line. 



Nos. 112, 113. These muscles appear to be branches from no. 20 to the lobes of 

 appendages (see fig. 3, PL LXXIV.). 



No. 114. Muscle of the Inner Lobe. — This muscle passes from the sclerite (a), in each 

 half of each appendage, to the extremity of the internal lobe. 



No. 115. Branch of 48, to sclerite (p) on anterior face. 



