384 Dr. Strahl on new Thalassine from the Philippines. 
compressed; they run out into a point in front, and bear on the 
outside the convex and pigmented cornea. The eye-peduncles 
are of the same length as the first jot of the mner antenna, of 
which the third joint is as large as the first and second together. 
The two flagella of these antennz are nearly of equal length: 
the external one is obliquely truncated in front, and somewhat 
bent outwards ; on its inside it is furnished with a row of long 
hairs. The inner flagellum is, as usual, about half as long as the 
thorax of the animal, and internally fringed with long hairs. 
The external antenna bears only a single flagellum; this is 
nearly twice the length of the thorax. The tuberculum occurs 
quite on the outer side of its jot, as usual in the genus Callia- 
nassa. The question whether Callianassa does or does not pos- 
sess anything of the nature of an antennal scale is a peculiar 
and difficult one. <A scale covering a larger or smaller portion 
of the peduncle of the antenna from above certainly does not 
occur; and yet the peduncle of the antenna is not three-jointed, 
but contains more joints. In order to understand this matter, 
it is necessary to examine more closely than has hitherto been 
usual into the structure of the antenne, and especially of the 
outer pair. 
I have already shown that the entire group of the Decapoda 
are divided into two great sections, according as there is at the 
base of the external antenna an operculum or a half-ring with 
the tuberculum. In the tubercular Decapods this half-ring is 
attached to the cephalothorax by means of a hinge-joit, and is 
slightly moveable. The articulation is effected externally to the 
carapace, and internally to the outer side of the frontal process 
of the epistomium. This half-ring, which we will call the zéer- 
calare, is interpolated into the attachment of the antenna to the 
cephalothorax : it is immediately followed by a joint, whith is the 
common supporter of the antenna and of the scale, and which I 
call the armiger; this bears the scale externally and the antenna 
internally, and often possesses a spine, as, for example, in the 
Lobster and the Cray-fish. In the Lobster, just after its escape 
from the egg, according to the careful observations of Kroyer, 
the scale-apparatus and antenna are suspended from a single 
common ring, but are separate* ; the latter 1s certaimly the inter- 
calare, although Kroyer does not mention that it bears the tu- 
berculum on its ventral surface. In the Cray-fish, at the same 
period, the scale-jomts and the antennal joints are, as I have 
noticed, more clesely approximated ; but it has the znéercalare, 
and, even several days before exclusion, a distinct tuberculum. 
Kroyer calls this piece pars basilaris, evidently followmg Milne- 
Edwards, who, however, uses the term article basilaire, without 
* Hippolyte’s Nordiske Acta, p. 43, taf. 6. fig. 134. 
