94 
THE VOYAGE OF H.M.S. CHALLENGER. 
labrum is near the middle of the carapace, which is narrow and elongated, exposing the 
fifth, sixth, seventh and eighth thoracic somites, and very much shorter than the elongated 
hind body. The carapace has a median dorsal spine, about as long as the antero-lateral 
spine, on its posterior edge, and there is a single acute straight spine on the lateral margin 
of the carapace, on each side, immediately anterior to the postero-lateral, the tip of which 
reaches nearly to the line of the anterior edge of the first abdominal somite. 
In the younger larvae the posterior edge of the carapace is transverse, and the telson 
is narrowed anteriorly, while in older larvae the carapace is deeply emarginated, and the 
lateral edges of the telson nearly parallel. In the oldest larva the inner spine of the 
uropod is longer than the outer, with a rounded lobe on its outer edge, the abdomen is 
depressed, about as wide as the carapace between the bases of the antero-lateral spines, and 
the postero-lateral angles of all the abdominal somites end in acute spines. 
This series, together with the gracilis series, gives a very complete picture of the 
changes which the Alima larva undergoes during its larval life. In the youngest stage 
which was observed (PI. VII. figs. 1 and 2) the shaft of the first antennae has only two 
joints, and the appendage ends in only two rami. There is no flagellum on the second 
antenna, and no appendages between the raptorial second thoracic limbs and the first 
pair of abdominal appendages. All the four thoracic somites are wider than long, and 
the third, fourth, and fifth are equal in length, and more than half as wide as those which 
follow. The abdomen is narrow, very slightly wider than the thorax, with five distinct 
somites, the last of which is short without appendages, while the appendages of the fourth are 
rudimentary. Those of the third, second, and first are functional, long and slender, with 
a long appendix interna. The tip of the labrum, which has no spine, is slightly anterior 
to the middle line, and the greatest width of the carapace is slightly less than its length. 
It narrows a little posteriorly, and its width between the bases of the postero-lateral 
spines is very slightly greater than its width between the bases of the antero-laterals. 
The width of the telson at its anterior end is about half the greatest width (see figs. 
1 and 2) and it is also slightly narrowed posteriorly. The posterior border, between the 
submedian spines (fig. 2) is straight and transverse, with about eighteen small spines. 
The intermediate spines are near the middle of the telson, separated by a slight 
interval from the laterals, and by a much longer interval from the postero-median, 
with some intervening dentations which are about as large as the primary spines. 
At the next stage (No, 3, fig. 4) the appendages are as before, except that the 
fourth abdominal appendages are larger, and the fifth pair are now present as rudiments. 
The position of the labrum and the shape of the carapace is essentially as in stage 2, 
and the telson is also nearly the same except that its posterior border is slightly 
emarginated. At the next stage (No. 4, fig. 5) the flagellum of the second antenna, 
the appendages of the third thoracic somite, and those of the sixth abdominal somite, are 
all represented by minute buds, and the third thoracic somite has become shorter than 
