100 THE VOYAGE OF H.M.S. CHALLENGER. 



is ample internal evidence, drawn from other structural features, to sliow that they are 

 Lysiosqidlla larvas ; and in addition to this indirect but satisfactory evidence, I am now 

 able to furnish more direct proof, as I have reared a Lysiosquilla, Lysiosijuilla excavatrix, 

 from one of those larvte (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, 

 mero-es into the Erichtlius 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 Erichthi, by the position of the postero-lateral spines of the carapace, which, when 

 seen in profile (PL X. figs. 7, 14; PL XL 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 

 l)y the great depth of the carapace, the lateral edges of which are ventrally infolded, as 

 shown in the figures. 



During their younger stages they exhiliit a most striking resemblance to the Alima 

 larva (PL XL 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 Squillie 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 Lysiosquilla, while the reverse is true without any exception in Alima and 

 in Squilla. 



The Lysioerichthus is a true Erichthus, although it is the most Alima-like 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 



