688 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXI. 



In all the specimens obtained the basal joint of these first antennt^ 

 was folded over beneath the ventral surface, as shown in the fig-ure. 

 That this is the normal attitude and not a folding due to pressure was 

 proved by examining some in an .open-watch glass, and by the fact 

 that many of the larvte in the subsequent chalimus stage showed the 

 same folding. 



The second antenna, unlike the first, have entirely lost their loco- 

 motor function and have become prehensile (fig. 11). Each now con- 

 sists of a long and stout basal joint, extending straight forward be3'ond 



the anterior margin of the 

 frontal plate, and an elon- 

 gated slender terminal claw, 

 which is bent over ventral ly 

 into a half circle. These sec- 

 ond antennas extend in front 



Fig. 5. — Mouth and second maxill.e of the meta- 



NAUPLU'S OF ALEBION GLABER. 



Fig. G. — FIK.ST maxillii'ED uf the 

 metanauplius of Alebion 

 glabek. 



of the carapace a distance equal to about half the length of the latter. 

 And when driven into the skin, the claws afford a powerful hold and 

 effectually protect the larva against removal ])y friclion or similar 

 cause. 



The mouth (fig. 5) has developed into a long proboscis hinged near the 

 center, inside of which, at the very tip, can be seen the mandibles. The 

 mouth opening is terminal, somewhat elongated, and surrounded by a 

 fringe of long hairs. On either side of the mouth tube at its base are 

 the second maxilla^ which at this stage consist of two entirely separate 

 rami of about the same size. Of these the endopod is short and stout 

 and slightly bifurcate at the tip, the outer branch being considerably 

 longer and larger than the inner. The exopod is made up of 

 two diverging slender spines joined together at the base. In this 



