82 
THE VOYAGE OF H.M.S. CHALLENGER. 
Although Claus decided that they are young Lysiosquillae they show their relationship 
to the genus Squittct as distinguished from Lysiosquilla by the following characteristics, 
all of which are shared by all fully-grown Alima larvae. The dactylus of the raptorial 
claw has on its inner edge a small number of marginal spines, usually about five or six ; the 
hind body is wide and flat, and the postero-lateral angles of the abdominal somites end 
in acute spines. The outer edge of the proximal joint of the uropod is bordered by a 
small number of spines, usually less than eight, and the inner one of the two spines on 
the ventral process from the posterior edge of the basal joint of the uropod is longer 
than the outer, and it has a tooth or lobe on its outer edge; and the telson has six 
marginal spines with minute secondary spines between the submedians, and four or 
more larger secondary spines between the submedian and the second or intermediate, 
and usually a single one internal to the base of the third or lateral marginal spine. 
While it is true that all of these characteristics are not exhibited by every adult Squilla, 
there are no Stomatopods except those of this genus in which they are all united, and 
they are all of them present in most Squillae and in all the Alimas. 
Joined to the fact that Faxon has reared a Squilla from an Alima, they indicate very 
clearly that the Alimse are Squilla larvae, and as we know of no other type of , larva 
which can be referred to this genus, the present state of our knowledge indicates that all 
Squillae have Alima larvae. As it can be shown very conclusively that the Alima is an 
Erichtlius, which has become accelerated in development and has dropped its Erichthoi- 
dina stage, and has become peculiarly adapted for a rapacious pelagic life, it is highly 
improbable that this change has taken place more than once, and as I shall give reasons 
for believing that it occurred very soon after the evolution of the genus Squilla, and that 
the larva of the most primitive of the true Squillae is an Erichthus- like Alima, the con- 
clusion that all the Alimse are Squilla larvae is warranted by the facts. The validity of 
these general conclusions can be better estimated after reading the descriptions of the 
larvae which follow, but these descriptions will be the more intelligible if an outline of the 
generalizations to be drawn from them be kept in mind. 
The Alima larva is characterised by the great elongation of the body, the possession 
of a flattened elongate 1 carapace, with the posterior median dorsal spine absent or rudi- 
mentary, the elongated abdomen and usually several of the posterior thoracic somites 
exposed behind the posterior edge of the carapace, by the very great elongation of the 
region between the antennae and the labrum, and by the fact that the eyes and eye stalks 
are usually exposed on the sides of the long slender rostrum. The carapace is narrow 
and its width is usually one-third or one-fourth of its length, although its total length 
makes a much smaller part of the total length of the body than it does in the Erichthus 
larva, as its increased length is more than overbalanced by the great elongation of the 
hind body. The older specimens of Alima are usually much larger than most of the 
Erichthus larvae, and the inner one of the two spines which project backwards from the 
