522 MR. W. B. S. BENHAM ON THE MUSCULAR 
this Memoir was in type; the reader is referred to his paper in Quart. Journ. Micr. 
Sci., Jan. 1884. 
2. Mesosomatic Entochondrites.—There are six of these, lying on the floor of the 
mesosoma on the hinder border of the bases of the appendages (see Pl. LX XII. for 
their position). The nerve-cord is dorsal to these entochondrites, and not below them 
as it is in the case of the plastron. They are more or less rectangular in shape, with 
their long axis transversely directed (Pl. LX XVI. fig. 8). The anterior and posterior 
corners are slightly produced, giving attachment to muscles. On the median ventral 
surface is a ridge. 
These have the same microscopic structure as the plastron. 
V. The Entapophyses. 
There are seven pairs of these, one on the thoracic carapace on its hinder vertical 
border, the rest in a line with these on the abdominal carapace. Lach consists of an 
invagination of the chitin to form a strong process, directed forwards, downwards, and 
slightly inwards; they are flattened from side to side. Several muscles are attached to 
each entapophysis ; thus, e. g., on the inner face, anteriorly, are attached the bundles of 
the oblique muscle (1, 2, 3); posteriorly, in the case of the last three, the ventral pygo- 
tergal (9); to the ventral edge, the posterior lamellar muscle (23) from the abdominal 
appendage of the same segment; on the outer surface, ventrally, the posterior lamellar 
muscle (22) from the succeeding abdominal appendage ; posteriorly, the dorsal pygal 
muscle (6). ‘To different entapophyses are attached different muscles. 
To the outer edge of each entapophysis is attached a half-ring of hyaline cartilage 
(capsuligenous tissue of Lankester) by the intervention of some fibro-cartilage (fibro- 
massive tissue of Lankester); by means of this ring some of the muscles from the 
abdominal appendages are attached. 
The fibro-massive tissue is continuous from each entapophysis to the next one, and 
forms a definite band-like structure on each side of the mesosoma, to which I give the 
name of “entapophysial ligament” (Pl. LXXIII. ec): it ends in the postabdominal 
sternite. i 
Microscopic Structure.—The entapophyses are similar to the carapace; the outermost 
layer of chitin-in the latter now, of course, lines the cavity which exists within the 
entapophysis: the layers are a good deal contorted, and are pierced by tubes in the 
same way as is the carapace. Some of these carry hairs, which project within the 
cavity. 
Below the chitin are seen the epidermic cells which produce the chitin. These are 
a good deal obscured by pigment. 
