ParKER AND Rich—Ox the Myology of Palinurus Edwardsit, Hutton. 175 
The antennule is further acted upon by two muscles which, unlike those of the 
other appendages, are continuous through the three podomeres, and may be con- 
veniently called the zz¢ternal and external long antennulary muscles. The external 
muscle arises by a calcified tendon from the arthrodial membrane close to the ventral 
edge of the articular cavity: the internal has a similar origin from the dorso-mesial 
aspect of the articular cavity. The external muscle is closely connected at its origin 
with the abductor, the internal with the adductor. Both muscles extend distad and 
send off slips to the proximal edges of the second and third podomeres and of the two 
flagella. In the middle of the proximal podomere their fibres are intermingled. 
The internal muscle seems to act as a combined adductor and levator of the antennule 
as a whole, the external as a combined abductor and depressor. Each flagellum is 
further acted upon by a small muscle which apparently serves as an adductor. 
Thus the muscles of the antennule resemble those of the abdomen rather than 
those of a typical appendage, since there are continuous bands extending through the 
whole appendage, arising from a fixed structure and sending off slips into the movable 
parts. 
9. Muscles of the eye-stalks (fig. 25). 
The eye-stalks are attached to the prostomial plate, a concave structure over- 
arched by the rostrum and the supra-orbital spines, and continuous externally with the 
carapace proper: its ventral border forms the dorsal edge of the articular cavity of 
the antenna, and the inter-antennulary bar is continuous with its mid-ventral region. 
It is perforated in the middle by a large transversely oval aperture, the ophthalmic 
fenestra, which forms the articular cavity for both eye-stalks, their loose arthrodial 
membrane being attached to its edges. The portion of the prostomial plate above 
this aperture is the supra-ophthalmic bar, it gives origin to the procephalic processes 
and is continuous with the ventral plate of the rostrum: the portion below the 
aperture is the 7zfra-ophthalmic bar, and gives origin to the clasping processes which 
embrace the rostrum laterally. The whole prostomial plate is lined by a strong sheet 
of ligament which, as already mentioned, gives origin to the anterior coxal ligament, 
and which is continued below into a chiasma-like arrangement of fibres connected 
with the inter-antennulary bar and covering the dorsal ends of the levator muscles of 
the antennules. 
The arthrodial membrane of the eye-stalks is calcified dorsally by a small median 
sclerite having the form of a half cylinder, and hidden in the entire animal by the 
rostrum to the concave ventral surface of which it is closely applied. A short 
distance on either side of this zxter-ophthalmic sclerite the arthrodial membrane is 
continued into the eye-stalk which consists of a small éasa/ sc/erite, ncomplete below, 
and of the strongly calcified dzsta/ sclerite or eye-stalk proper. 
