MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 357 



Stomatopod larva' or Erichthidae, as they were named before their larval nature was suspected, 

 have been divided iuto four genera, Erichthoidina, Krii'htlnts, NqHtllcrichthiis, and Alima. Of these 

 four the lirst, Erichthoidina, is simply a younger stage in the life of the Erichthus, and the third, 

 Squilk'rk'hthus, a fully-grown larva of the Erichthus type, so that the genera become reduced to 

 two, Erichthus and Alima. Of these two genera, one, Alima, is much more sharply defined than 

 the other, Erichthus, which contains a number of divergent types, of which I have shown that 

 five may be clearly distinguished, and I have proposed, for these five, names which indicate the 

 adult genus to which each corresponds. I have shown that there are many reasons lor believing 

 that all Aliml are Squilla larva}; Alimerichthus, the larvae of Ghloridella; ErichthaUma, the larva; 

 of Coronida; Lysierichtlius, the larvae of Lysiosquilla, and Pseuderichthus, the larvae of Pxeudo- 

 squilla. The remaining larval type may be distinguished from the Lysierichtlms by the shallow- 

 ness of it's carapace, which is not at all infolded, and by the position of its postero lateral 

 spines, which arise very close to the dorsal middle line; while it may be distinguished from the 

 Pseuderichthus larvae by the length of the posterolateral spines, which are at least half as long as 

 the carapace, and also by the fact that the telson is wider than long and longer than the long 

 outer spine of the uropod. For this larval type, which was represented in the Challenger collec- 

 tion by many specimens, I proposed the name Gonerichthus, giving, at the same time, many 

 reasons for regarding it as the larva of the genus Gouodactylus. Several of these larvae were 

 selected and shown in PI. XII, Fig. 5, PI. xm, Fig. 9, and PI. XV, Figs. 1 and 5, of my report; and 

 I pointed out that in all of these larvae, as in the young Gouodactylus, the sixth abdominal somite 

 has a pair of submediau spines near its posterior edge, and its posterolateral angles are produced 

 into acute spines. The telsou is slightly wider than long, and its submedian spines are long and 

 slender, but shorter than they are in Pseuderichthus. The telson is notched on the middle line, 

 and there are from fourteen to twenty small secondary spinules on its posterior edge, between the 

 submedians. There is one small secondary spinule internal to the base of the lateral marginal 

 spine, another internal to the base of the intermediate, and a third midway between this and the 

 submedian. 



In PI. xv, Figs. 5 and G, of my report, as in the young Gonodactylus, the outer edge of the 

 proximal joint of the exopodite of the uropod is fringed by nine marginal spines, the terminal one 

 longest, and the outer spine of the basal prolongation is much longer than the inner, but 7iot so 

 long as it is in Pseuderichthus. A comparison of the telson of the young Gonodactylus with that 

 of the other larval types will show that the one now under discussion is the only one which exhibits 

 this resemblance, and as this larva never exhibits any traces of marginal spines on the dar.tyle of 

 the raptorial claw it must pertain to some known adult with an unarmed dactyle or else to a new 

 geutis. It is not probable that a larval type which is so common pertains to an unknown adult 

 genus. The larvae are not Protosquillir, as this genns has the telson fused with the sixth abdom- 

 inal somite, while it is free in the older larvae; nor are they PseudosqitiUa', for they have no movable 

 spinules on the tips of the submedian spines of the telsou; and as all the other genera of Stoma- 

 topods except Gouodactylus have the dactyle armed, the only remaining genus is Gonodactylus, 

 and the structural characteristics of the oldest larva? indicate that they are the young of species 

 in this genus. 



Led by these considerations I did not hesitate to speak of these larvae, in the Challenger 

 report, as Gonerichthi, or young Gonodactyli, and to give this larval form as one of the diagnostic 

 characteristics of the genus. This determination rests, however, upon circumstantial oT indirect 

 evidence; and, while the evidence is quite conclusive, I was nevertheless pleased to obtain more 

 positive proof from the larva' which I reared from the eggs of Gonodactylim chimi/m. 



Like many other Crustacea which inhabit the coral reefs, this species has its metamorphosis 

 abbreviated and it hatches from the egg in an advanced condition. It is shown just before hatching, 

 seen from behind in PI. xiv, Fig. ], and from in front in Fig. 2. The large yolk covers the dorsal 

 surface, and the larva is doubled on itself, so that the telson and the tip of the abdomen are visible 

 in a front view. The first five abdominal somites are indicated before it leaves the egg, and the 

 first five pairs of abdominal appendages are fully developed, although the other appendages, with 

 the exception of the mandibles and the large raptorial second maxillipeds, are either absent or rudi- 

 mentary, The eyes are large, and even before hatching they are movable, although they are 

 nearly sessile. 



