PACKARD. ] “MORPHOLOGY OF PHYLLOPODA. 391 
The axis of the second pair of beenopods is composed of two joints, 
but we should not agree with Lankester’s notation of the joints; the 
joint marked 1 includes what corresponds to aa! and az’ of the first leg; 
and his joint 2 (ax?) corresponds to ax’ and az‘ of the first leg; in other 
words, of the two divisions of the axis of the second leg the tirst repre- 
sents the two basal joints of the first leg and the second the third and 
fourth. So it seems to us the “joints” are more or less arbitrary sub- 
divisions of the axis, and are not, properly speaking, true joints, hence 
we would call them pseudo-joints or subjoints. 
Beginning with the endites, the first is transformed into a large, broad, 
thick, squarish lobe, whose inner edge is beset with dense fine, stiff sete. 
This is the gnathobase of Lankester, and what we have called the coxal 
lobe (Plate XIX, fig. 3, elsewhere cl, or '). The gnathobase of each limb 
is diverted outward and backward, and thus, with those of the other 
limbs, forms a long series bordering the median sternal line of the body 
behind the mouth-parts, and which, as in the Limnadiade, serves to re- 
tain the food and to push it toward the mouth and jaws. 
We should not, as Professor Lankester appears to do, say that “a 
similar feature is characteristic of Limulus.” The set of stiff spines in 
the Merostomata are developed directly upon the coxopodite or basal 
joint of the limb, which is directly homologous with the coxopodite of a 
crab, the resemblance to that of Apus is one only of analogy, though a 
very interesting one; the function, of course, being the same in each. 
The succeeding five endites of the first pair of limbs are similar im 
form, being subjointed, the joints not, however, being complete and not 
movable upon each other, the sutures marking them only extending 
part way towards the middle of the process. The third, fourth, and 
fifth endites, particularly the fifth, are remarkably long and antenni- 
form. The sixth forms a minute pointed scale, whose base is confluent 
with that of the fifth. 
The gill in the Apodide is rather small and pyriform; while the fia- 
belium is very simple in form compared with the Limnadiade, but still 
well provided with muscles, and, as in the latter family, forming the 
principal swimming as wellas respiratory orgaus. They are triangular, 
the outer end rounded, the inner pointed and somewhat produced, but 
there is no such interesting differentiation in form and function as occurs 
in the Limnadiad flabellum. 
Both exites and endites are remarkably persistent in form in the dif- 
ferent species and are not of much use in taxonomy. 
In the larva, 25™™ long, of Apus lucasanus, as drawn by Gissler (Plate 
XXXV, fig. 7), which corresponds well with Claus’s drawing of the 
same stage in Apus cancriformis I have added the references to the 
pseudo-joints (az!-az*). The gnathobase has two series of spines, the inner 
short; the sixth endopodite is seen to be very long and slender, while 
it is minute, short, and broad in the adult. The two spines at the end 
are noticeable, as there are four small ones in Claus’s drawing. The 
flabellum is very much smaller than in the adult, while the gill is but 
little larger. 
podite, and epipodite, supported on a protopodite or basal division (fig. 63 D, 4.1). 
The latter consists of three joints—a coxopodite produced internally into a strongly 
setose prominence (not represented in the figures), a basipodite, and an ischiopodite, 
the latter elongated internally into a lanceolate process, and bearing on its outer 
side two appendages, of which the proximal—the epipodite or branchia is pyriform 
and vesicular in specimens preserved in spirits. The distal appendage which appears 
to represent the exopodite (6) is a large flat plate, provided with long setz on its 
en Huxley did not find the maxillipedes and second antennz in Lepidurus 
glacialis, 
‘ 
