THE CEPHALOTHORAX. 151 
pleurobranchia (fig. 4, plb. 14) is attached; and in 
front of this, it is connected, by a narrow neck, with 
an elongated triangular piece, which takes a vertical 
direction, and lies in the fold which separates the posterior 
thoracic somite from the next in front. The base of this 
cpe. xy. 
Fig. 38.— Astacus fluviatilis —The mode of connexion between the last 
thoracic and the first abdominal somites (x 5). «, L-shaped bar ; 
cpe, carapace ; cap. 14, coxopodite of the last ambulatory leg ; pld., 
place of attachment of the pleurobranchia ; st. XV, sternum, and 
t. XV, tergum of the first abdominal somite. 
piece unites with the epimeron of the penultimate somite. 
Its apex is connected with the anterior end of the horizontal 
arm of an L-shaped calcified bar (fig. 38, a), the upper end 
of the vertical arm of which is firmly, but moveably, con- 
nected with the anterior and lateral edge of the tergum 
of the first abdominal somite (t. XV.). The tendon of one 
