Parker and Ricu—Ox the Myology of Pahnurus Edwardsi, Hutton. 177 
4. The muscles of the tail fin are very complex, several bands passing between 
the telson and the lateral tail-lobes, and so serving to approximate the parts of the 
fin during extension of the abdomen. 
5. The mandible is acted upon by three adductors and two abductors. 
6. Two pairs of muscles and two pairs of ligaments probably formed by the 
degeneration of muscles, are described passing between the axial skeleton and the 
pseudepistoma or fused coxopodites of the antennze. 
7. The antennule has a unique form of articulation allowing of movement in all 
directions. It contains two muscles, their fibres partially united, which arise from 
the axial skeleton and extend through the whole length of the appendage, sending 
slips to the various podomeres. The musculature of the antennule thus resembles 
that of the abdomen rather than that of the other appendages. 
DESCRIPTION OF PLATES. 
PLATE XVII. 
Fig. 1.—Two abdominal segments with the terga removed to show the extensor muscles: in the lower 
segment the superficial extensors are removed. 
Fig. 2.—Two abdominal segments with the intersternal membrane removed to show the superficial flexors. 
Fig. 3.—Three abdominal segments with the exoskeleton removed from the left side to show the insertions 
of the oblique extensors and flexors. 
Fig. 4.—Adjacent portions of the cephalothorax and abdomen, showing the rotator muscle and tlie 
insertions of the oblique extensors and flexors: the outline of the central muscle is dotted. 
Fig. 5.—Frozen sections through the thorax. 
Figs. 6 and 7.—Two frozen sections through the abdomen. 
PLATE XVIII. 
Fig. 8.—Dissection of the ventral muscles of the abdomen as exposed by the removal of the dorsal muscles, 
enteric canal, &c. On the left side portion of the enveloping muscles is removed to show the 
centrals. In the upper part of the figure the muscles of the antennz, mandibles, &c., are shown. 
Fig. 9.—Dissection of the ventral muscles of the abdomen from beneath. On the left side the longitudinal 
flexors are partly cut away so as to expose the transverse muscles, and the oblique flexors are 
displaced. 
a 
