30 DR. G. C. BOURNE ON THE RANINID^ : 
The succeediiio- ganglion pair, supplying the first pereiopods, is situated well 
back in the thorax, and is connected with the pair supplying the chelipeds by 
two long connectives separated from one another by a well-marked interval. 
The ganglion-pair of the second pereiopods is united with the preceding pair 
by similarly distinct connectives, but only one-third as long as those con- 
necting the chelipeds and tirst pair. The connectives between the second 
and third ganglion-pairs oil the pereiopods are shorter, but set widely apart, 
leaving an oval space for the passage of the large sternal artery. The two 
last thoracic ganglion-pairs, supplying the third and fourth pereiopods, are 
fused together, and the connections between them cannot be distinguished, 
but the separate ganglia can be clearly^ recognized, f )losely applied to the 
last thoracic ganglion-pair is the chain of abdominal ganglia, completely 
withdrawn into the thorax and represented by a short and thick nervous mass 
divided by distinct transverse consbrictions into five segments. The terminal 
segment apparentlj^ represents the fifth and sixth abdominal ganglia fused 
together. Paired nerves issue from each abdominal ganglionic segment, ajid 
pass backwards closely bound up in the same connective-tissue sheath as the 
fused mass of abdominal ganglia, but they are represented as spread out by 
dissection in fig. 8. The nerves issuing from the first abdominal gnnglion 
segment can be traced to the first pair of modified copulatory abdominal 
limbs of the male. In this condensed and abbreviated representative of the 
abdominal nerve chain no trace of connectives nor of ihe paired stucture of 
the ganglia can be detected, The abdominal ganglia and the nerves passing 
from them to the abdomen lie in the concavity of the narrow sella turcica 
posterior formed by the deeply infolded sternal apodemes of the last two 
thoracic segments. PL 4. fig. 10 is a representation of the ventral nerve 
chain oi Lyre'idus tridentatus. The general plan is similar to that oi Rahina, 
but the details are different. Tiie suboesophngal gnnglion is an ovoid mass, 
formed by the fusion of the ganglia of the mandibles, maxillae, and niaxilli- 
peds. As I could only count five nerves given off tVona this ganglion on 
either side, I conclude that the mandibular nerve issues, as in Ranma, from 
the circum-oesophageal connectives, but I was not able to verify this point. 
The ganglion-pair of the chelipeds instead of being approximated to the 
oesophageal as in Raniiia, is placed farther back in the thorax and is united 
with the subresophageid hj a thick cord, in which I could not trace any 
separation of the connectives in the middle line. My specinien was none 
too well preserved, but I can say for certain that these connectives are bound 
together in the same connective-tissue sheath. The ganglion-pairs of the 
chelipeds and first pereio2iods are distant and, as in Ranina, their connectives 
are separated by a distinct slit-like space. The posterior thoracic ganglia 
are more closely approximated than in Ranina, and the short connectives 
between the ganglion-pairs of the first and second pereiopods are bound 
