438 MR. P. H. GOSSE ON THE STRUCTURE, FUNCTIONS, AND HOMOLOGIES 
which, again, the left is considerably larger than the right. The lorica, in Mon. 
ratt.ii.'i, and much more prominently in Mast, carinata, is furnished with a dorsal 
Carina, running along the median line; the elevation of this ridge is not perpendi- 
cular, but leans considerably over to the right side. Even the single foot-spine, which 
is so characteristic of the genus, must be considered either as representing the ordi- 
miry pair soldered together, or as single through the obsolescence of the other. That 
the latter is the true solution is the more probable, since, in Mastigocerca, there is, 
at the base of the foot-spine, another spine, very minute, but distinctly jointed to the 
foot-bulb. This unsymmetrical development is not without parallel in higher animals ; 
of which it will be sufficient to allude to a single example, in the case of the pro- 
jecting tooth of the Narwhal. 
92. The figure of the incus fulcrum in Monocerca porcellus, and the obsolescence 
of its ra7ni, make an approach to the structure which we find in a very curious form, 
Scaridium longicaudum (Plate XVII. figs. 64, 65). The whole organization of the 
manducatory apparatus is here so abnormal, that I shall describe it in detail ; espe- 
cially as Dujardin has not noticed the genus at all, and Ehrenberg confines him- 
self to the vague remark, that “ the Schlundkopf is oblique, with unequal, 
pincer-toothed (one-toothed) jaws.” 
93. The mastax is somewhat obconic, or shaped like the heart of a mammal ; a 
muscular sac, on the parietes of which transverse rugce appear (/3). The eye (j 7), a 
large flattened capsule, with the crimson pigment not quite filling it, is attached to 
its occipital surface; apparently not connected, as usual, with the large occipital 
ganglionic sac {y) ; which, however, presses upon it from above and behind. The 
summit of the mastax projects into a point, which, though within the level of the 
ciliated ridges of the front (fig. 64), seems to be in contact with the surrounding 
M^ater, without the intervention of a buccal funnel. This point is cleft deeply; the 
incision being transverse, from right to left, but obliquely upwards (fig. 65). The 
occipital division separates widely from the mental one, with a gaping or snapping 
action, very frequently performed ; but with so great a rapidity and suddenness, that 
it needed long-continued observation to enable me to understand the parts. The 
structure is as follows. 
94. Behind the occipital division, and from its point, spring several arched setse ; 
and an apparatus of hooked teeth is visible within its concavity. The mental divi- 
sion (^) is slightly bifid, with rounded points ; between which, at the moment of 
gaping, several hooked setse are projected, and instantly retracted (s). These setse, 
or teeth, are connected, by prolongations of their bases, which are doubly geniculate 
and appear jointed, with the summit of the fulcrum (g) ; and must therefore be the 
representatives of the rami. The fulcrum itself is a straight rod, with a strongly 
developed carina (h), arcuated somewhat in the same way as that of Notommata 
(lurita (see fig. 17). 
95. The mallei consist each of a thin uncus (e), working on the j'atnus, and of a 
