AND ENDOSKELETAL SYSTEMS OF LIMULUS. ‘ 327 
on the level of the third coxo-tergal (the second large muscle seen on opening the 
animal), but nearer the median line. 
No. 25. The Tergo-coxals of the second, third, fourth, fifth, and sixth Pairs.—A large 
muscle, short, but thickening rapidly, is attached to the rounded knob at the top of the 
ring formed by the two borders of the entocoxite of each of the five following proso- 
matic limbs (25 a, 256, 25, 25d, 25e). They arise from the carapace in order one 
behind the other (Pl. LX XVI. fig. 1 and fig. 7, also Pl. LX XIII). 
No. 26. Antero-superior Tergo-coxal Muscles. 
No. 27. Antero-inferior Tergo-coxal Muscles. 
No. 28. Postero-superior Tergo-coxal Muscles. 
No. 29. Postero-inferior Tergo-coxal Muscles. 
These four sets of muscles are found in connexion with each of the five pairs of pro- 
somatic appendages succeeding the first. They are inserted into different parts of the 
entocoxite of each limb, as shown in Pl]. LX XVI. fig. 7, and arise from arew on the 
carapace surrounding the origin of the muscles 25 a, 25 6, 25 ¢, 25d, and 25e. 
No. 30. Anterior Plastro-coxal Muscle.—A muscle attached to the inner ventral face 
of the anterior cornu of the prosomatic entochondrite, and passing forwards is inserted 
into the anterior face of the rod-like entocoxite of the first prosomatic appendage. 
No. 31. Posterior Plastro-coxal Muscle-—A muscle arising behind no. 30, from the 
entochondrite, also goes to the entocoxite of the first appendage, but is inserted below 
no. 30. 
No. 32. Superior Plastro-coxal Muscle-—A muscle arising from the outer face of the 
anterior cornu of the prosomatic entochondrite, passes slightly forwards, enters the space 
bounded by the two borders of the entocoxite of the second limb; it here breaks up 
into two—m going to the inner face of the anterior, 7 to the inner face of the posterior 
border. Here they each spread out, passing upwards; they do not go far into the 
coxa. For this and nos. 33, 34, see Pl. LX XVI. fig. 7. 
No. 33. Mid Plastro-coxal Muscle.—This muscle rises below no. 32 from the ento- 
chondrite, and passes slightly forwards; it is inserted into the posterior border of the 
entocoxite of the second limb. 
No. 34. Inferior Plastro-coxal Muscle-—Rises behind and below no. 33 from the 
under-surface of the body of the entochondrite, and passing forwards, below no. 33, is 
inserted into the anterior border of the entocoxite of the second prosomatic limb. 
No. 35. ( 0, its anterior; p, its posterior branch. 
No. 36. | These muscles go to the third prosomatic appendage, and have a similar 
No. 37. | course to nos. 32, 33, 34. 
No. 38. This muscle is similar to 32 and 365, rises behind them, and goes to the 
fourth appendage: gq, its anterior; 7, its posterior branch. 
No. 39. This muscle passes in a more backward direction from its origin in the edge 
of the entochondrite to the fourth entocoxite (corresponds to 33). 
VOL. XI.—PART x. No. 3.—ay, 1885. 3D 
