436 J. J. LISTER. 



hatched. The youngest known member of this series of forms^ 

 the Eri chthoidina, is represented in fig. B. 



The carapace is furnished with spines resembling those of 

 the larva shown in fig. A, and well-developed compound eyes 

 are present. The first antennae are obscurely biramous, while 

 the second are uniraraous. The thorax is distinctly seg- 

 mented, and the five anterior segments bear biramous swim- 

 ming feet, while the three following segments are without 

 appendages. The first pair of abdominal feet are present, but 

 behind the segment bearing them, the abdomen is unseg- 

 mented, and ends in a large truncated telson. 



In succeeding stages the Erichthoidina larva changes into a 

 Zooea-like form comparable with the Alima larva of Squilla 

 and Gonodactylus, but the stages which precede the Erich- 

 thoidina are unknown. 



Now the development of the Erichthus larva differs from 

 that of the Schizopod and Decapod larvae with which we are 

 acquainted, in one respect, among others, namely, that in a 

 stage, the Erichthoidina, antecedent by many moults to the 

 Zooea stage, the paired eyes are already well developed. In this 

 respect, as well as in the shape and large size of the carapace, 

 the disposition and direction of its spines, and in the fact that 

 it is a reduplication exclusively of the cephalic region, the 

 larva under consideration resembles the Erichthoidina. 



I would submit then, that it is rather probable that this larva 

 is a Stomatopod larva at a stage prior to the Erichthoidina 

 stage ; that it is, in fact, a Stomatopod metanauplius. 



The condition of the antennae, the first apparently simple, 

 and the posterior biramous, difi'ers from that found in the 

 Erichthoidina stage, but the difference is precisely that which 

 from analogy with other nauplii we should expect to find in 

 the metanauplius form. The first antenna of the stage figured 

 by Hansen appears to be just acquiring its biramous character. 

 The larva appears to be unique among those hitherto de- 

 scribed in possessing well-developed compound eyes in the 

 metanauplius stage. The articulated condition of the divi- 

 sions of the caudal fork is also, so far as X know, peculiar 



