264 Proceedings of the Royal Society of Edinburgh. [Sess. 
Taken altogether, these various articulations allow the head to be bent to 
an angle of 80 degrees with the lateral border of the pleon. At the articu- 
lation between the cephalosome and the second true thoracic segment the 
soft intersegmental cuticle has disappeared. 
On the whole, the body is very compact and rigid ; in particular, it 
allows of no elongation or longitudinal separation of segments, as does that 
of Ligia — see Tait (1917, I). It is the less surprising, then, to find that 
the thoracic sternites are thin and flexible, and that, with the exception of 
the last segment, their calcareous skeleton is divided in the middle line — see 
fig. 2. This peculiarity, indicated in one of Eights’ original figures, seems 
to have attracted slight attention, Pfeifer (1887) alone referring to it. A 
similar arrangement, in this case affecting segments 2 to 7, is present in 
Fig. 8. — Seventh true thoracic somite of G-lyptonotus from the front. Natural size. 
To show the ventral inturnings of the anterior border of the tergite. 
Ghiridotea, Harger; see plate iv, fig. 2 in Gerstaecker, or fig. 374 in 
Richardson (1905). It may with considerable reason be interpreted as a 
device for allowing of distension of the body after a meal ; in females with 
ripening ovaries the ventral wall does in reality protrude, and in this 
connection it may be mentioned that the length of a specimen of Ligia 
at the time of capture is frequently greater than after a sojourn of some 
days without food. 
We have already had occasion to refer to the ventral inturning of the 
anterior border of each thoracic termite. This does not involve the border 
in its medial but only in its more lateral part — see fig. 8. Owing to the 
presence of these inturnings the lateral portion resists any bending in the 
main plane of curvature of the tergite, as when the ring as a whole is 
compressed from side to side. The middle portion of each tergite is 
flexible, and in consequence of the additional medial splitting of the 
sternite each segmental ring when detached (with the exception of the 
very last, which possesses a rigid sternite) can be readily compressed 
from side to side 
Owing to the absence of ventral inturning on the middle part of each 
tergite, space is provided for the dorsal longitudinal muscles, which lie a 
short distance on each side of the middle line. As in the thoracic segments 
