100 
THE VOYAGE OF H.M.S. CHALLENGER. 
is ample internal evidence, drawn from other structural features, to show that they are 
Lysiosquilla larvae ; and in addition to this indirect hut satisfactory evidence, I am now 
able to furnish more direct proof, as I have reared a Lysiosquilla, Lysiosquilla excavatrix, 
from one of those larvae (PL X. figs. 14, 15), and one of the Challenger specimens 
(PI. X. fig. 7) exhibits the characteristic transverse pigment stripes and other specific 
characteristics of Lysiosquilla maculata, while another advanced larva of this type 
(PI. XI. figs. 6, 8, 9) exhibits the flattened oval thin membraneous appendages to the 
exposed thoracic limbs which is characteristic of the lower Lysiosquillse. 
This larval type, for which I propose the provisional generic name Lysioerichthus, 
merges into the Erichthus of Gonodactylus and that of Pseudosquilla in such a way 
that it is often difficult to decide whether a certain larva is to be referred to the one or 
the other of these groups, but the Lysioerichthus may usually be distinguished from the 
other Ericlithi, by the position of the postero-lateral spines of the carapace, which, when 
seen in profile (PL X. figs. 7, 14; Pl. XI. figs. 2, 3) are separated by a wide interval 
from the dorsal middle line ; they are either on the ventral edge of the carapace or else 
they are much nearer to it than to the dorsal middle line, while the reverse is the case 
in the Erichthus of Pseudosquilla (Pl. XII. fig. 6) and that of Gonodactylus (Pl. XV. 
figs. 11, 12). In addition to this feature, which is, I believe, strictly diagnostic, they are 
also characterised among the Erichthi by the width and flatness of the hind body, and 
by the great depth of the carapace, the lateral edges of which are ventrally infolded, as 
shown in the figures. 
During their younger stages they exhibit a most striking resemblance to the Alima 
larva (Pl. XI. fig. 1 ; Pl. XII. fig. 4), although this resemblance is entirely lost by 
the older larvae. 
In addition to the greater number of spines on the dactylus of the raptorial claw they 
are also distinguished by other features, all of which indicate their identity with 
Lysiosquilla. The telson is wider than long, like that of Lysiosquilla, and unlike that of 
Alima and Squilla, where it is, almost without exception, longer than wide ; and between 
its intermediate and submedian marginal spines there is usually only one secondary spine, 
and never more than four. This is true of the adult Lysiosquilla also, while in all the 
adult Squillae and all the Alimse the secondary spines are more numerous. 
The outer one of the two spines at the end of the ventral prolongation from the base 
of the uropod is, with rare exceptions, longer than the inner, as is the case, also with rare 
exceptions, in I/ysiosquilla, while the reverse is true without any exception in Alima and 
in Squilla. 
The Lysioerichthus is a true Erichthus, although it is the most AlimaAdke, of the 
Erichthi. Like the Alima the young Lysioerichthus has numerous marginal spines on 
the lateral edges of the carapace, although this characteristic disappears as the larva 
grows older, while it is retained by the fully grown Alima larva. In the very young 
