A REMARKABLE ORUSTACEAN PARASITE, 113 
A larze digastric occlusor muscle lies on the ventral side of 
the stomodeum, close to its entrance into the intestine, and 
just in front of the gland of unknown significance mentioned 
above. It is omitted in the diagrams for clearness sake. 
RELATION OF PeTRarRcA TO LAURA AND TO SYNAGOGA :—THE 
ASCOTHORACIDA, 
Of Synagoga, we have at present only the short preliminary 
account by Norman (‘ Rep. Brit. Assoc.,’ 1887, p. 86), dealing 
merely with the external characters. From this it appears 
that it strongly resembles Laura, but that the appendages have 
undergone less degeneration. 
_ Laura gerardiz! (‘Mem. Ac. Sci. Instit., France,’ xlii, 
160 pp., vill pls.) is parasitic on, and overgrown by, the polyps 
of Gerardia, an Antipatharian genus from the Mediterranean 
coast of Africa, It is adherent to the stock of its host by a 
remarkable development of processes on the carapace, which 
grow in among the tissues of Gerardia, and are probably 
nutritive in function. The carapace is an elongate sac within 
which the animal lies (1. c., pl. i, figs. 1, 2) and is thus formed : 
a narrow stalk-like outgrowth from the head? becomes almost 
at once an enormous fan-shaped expansion (l.c., pl. ui, fig. 15; 
pl. i, fig. 25), measuring up to 4 cm. in length; and the two 
expansions fuse along the dorsal and ventral lines except for 
one small opening. The animal, generally less than 1 cm. in 
length, is to be found near this opening, towards which both 
cephalic and anal regions are directed ; it is divisible into the 
following regions (l.c., pl. ii, fig. 25): (1) a large dome- 
shaped swelling, regarded by Lacaze-Duthiers as the head [but 
which is probably an exaggerated buccal cone]; it is grooved 
ventrally and anteriorly, and at the summit of the groove is 
placed the buccal armature, an arrangement of styliform pieces 
1 Matter additional to Lacaze-Duthiers’ original description is enclosed 
in square brackets. 
2 Query: on each side? Neither from the figures nor description have I 
been able to infer with certainty whether one median dorsal or two dorso- 
lateral outgrowths give origin to the carapace. 
