AND ENDOSKELETAL SYSTEMS OF LIMULUS. 329 
IV. Muscles connected with the Plastron or Prosomatic Entochondrite not described 
in the preceding Sections. 
No. 49. The Tergo-proplastral Muscles ( Anterior Plastro-tergals)—This muscle (rand7) 
is inserted into the inner side of the anterior cornu of the plastron, and passes out- 
wards, upwards, and forwards to its attachment to the carapace, slightly in front of and 
mediad of the muscle 25. 
No. 50. A smaller muscle, inserted behind 49, passes slightly forwards and upwards, 
in front of 24, to its attachment to the prosomatic carapace. 
No. 51. Similarly inserted, passing behind 24 to its attachment to the carapace, 
behind and mediad of the third coxotergal (25 ). 
No. 52. The Dorso-lateral Plastro-tergal—tThis (r and 1) is inserted into the dorsal 
process of the entochondrite, passes backwards, upwards, and outwards across no. 18, 
and is attached to the carapace in the same line with this latter muscle. 
No. 53. The Dorso-lateral Entapophysio-plastral.—This muscle (r and /) is inserted 
on the hinder edge, near the base, of the dorsal process of the plastron, and passes 
upwards and backwards, and only very slightly outwards, crossing the attachments of 
no. 2, to the first entapophysis, to the anterior inner edge of which it is attached. 
No. 54. The Anterior Entapophysio-mesoplastral Muscles.—Each of these (r and 1) 
rises along the middle line of the dorsal surface of the “body” of the plastron, and 
passing across the attachment of no. 2, outwards, and slightly backwards and upwards, 
is attached to the first entapophysis alongside 53. 
No. 55. The Posterior Entapophysio-mesoplastral Muscles.—Kach (r and 1) rises from 
the base of the posterior process of the plastron, and passing outwards, across no. 2, 
goes to the first entapophysis, to which it is attached close to 54. 
No. 56. The Posterior Entapophysio-metaplastral Muscles.—Each (r and /) rises 
below 55, from the side of the posterior process, and passing outwards and backwards 
crosses no. 2, and is attached to the second entapophysis. 
No. 57. The Lateral Tergo-proplastral Muscles.—A short muscle (r and /) is inserted 
into the distal end of the anterior lateral cornu of the plastron, and is attached to the 
carapace between nos. 25 (4 and ¢), but outside the line formed by these muscles. 
No. 58. A similar muscle (7 and /) is inserted into the posterior lateral cornu, and is 
attached behind 57, between 25, ¢ and d. 
No. 59. A small muscle is inserted a short way down the posterior lateral cornu, and 
is attached to the carapace close to 25 (d). 
No. 72. The Vertical Entapophysio-metaplastral Muscles—Kach (r and ) rises 
below 56, from the edge of the posterior process of the plastron, and passes to the third 
entapophysis. 
No. 67. Plastro-buccal Muscle—From the under-surface of the entochondrite, a few 
muscular fibres go to the cesophagus close to the mouth. 
3D 2 
