342 MISS E. J. BECK ON THE MUSCULAR 
In the first appendage the posterior portion of the coxal sclerite 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 (EK) is larger than that of 
the third appendage and has a more 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 which runs posteriorly in a horizontal plane. It is 
marked in fig. 16, Pl. 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 (KX) 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 metasternite, 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 (Pl) or Prosomatic Entochondrite (Entosternite of Lankester, /oc. cit.). 
—Towards the posterior part of the prosoma, between the cephalothoracic plate and 
the sternal surface, is situated the plastron (Pl. LX XX. 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 (Pl. LX XX. 
fig. 14, snp) 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 
