342 MISS E. J. BECK ON THE MUSCULAR 



In the first appendage the posterior portion of the coxal sclevite is drawn out into 

 a narrow and long process (A), which extends backwards and gradually tapers to a 

 point. 



In the second appendage the anterior margin of the coxal sclerite presents on its 

 inner face a small process (B) which points down towards the posterior margin of the 

 same sclerite. 



In the third appendage the coxal sclerite is drawn out internally into a process on 

 both the anterior and posterior margins. That on the anterior (C) is very small and 

 is near the median line ; that on the posterior (D) is large and is situated laterally. 



In the fourth appendage there are also two internal processes on the coxal sclerite, 

 the one anterior, the other posterior. The anterior process (E) is larger than that of 

 the third appendage and has a move lateral position. The posterior process (F) is 

 similar to that of the third, and is lateral. 



In the fifth appendage there is a small process (G) on the anterior margin of the 

 coxal sclerite, which is quite lateral and behind the posterior process of the fourth 

 appendage. There is no process on the posterior margin of this sclerite. 



The coxal sclerite of the sixth appendage carries no process on either margin. 



Median Entosclerites. — In the median line anterior to the mouth is situated an 

 entosclerite (H), to the anterior portion of which the superior portion of the coxal 

 sclerite of the second appendage is articulated. From either side of this anterior 

 portion there is a lateral process M'hich runs posteriorly in a horizontal plane. It is 

 marked in fig. 16, PI. LXXIX., by the figures appropriate to muscles which are 

 attached, viz. 95, 96, 97. This entosclerite may be called the " preoral entosclerite." 



A small entosclerite (K) is situated in the median line close behind the mouth ; on 

 it the inferior portion of the second appendage, and the third and fourth appendages, 

 are articulated. This may be called the " postoral entosclerite." 



Posterior to this in the median line lies the pentagonal thoracic metastemite, on the 

 internal surface of which is a narrow process (L) standing up in the middle line. This 

 process soon forks and ends anteriorly to the genital operculum. This may be called 

 the " carino-sternal entosclerite." 



The Plastron (PI) or Prosomatic Entocliondrite (Entosternite of Lankester, loc. cit.). 

 — Towards the posterior part of the prosoma, between the cephalothoracic plate and 

 the sternal surface, is situated the plastron (PI. LXXX. fig. 13). The alimentary canal 

 passes through it in a canal (GC) which lies between two dorsal ridges running on the 

 dorsal surface from the anterior to the posterior portion. The nerve-cord also runs 

 through a canal (NC) in the plastron, and thus forms a subneural portion (PI. LXXX. 

 fig. 14, sn,})) on the ventral side. The anterior aorta also perforates the plastron by 

 the canal AC. The muscles 65 and 83 also perforate the lateral regions of the plastron. 

 This entochondrite is not fixed to any of the chitinous skeletal pieces, except by muscles 

 and fibrous tissue. At its posterior end there is a large posterior flap {pf), which is 



