310 BULLETIN OF THE 



pound eyes are of huge dimensions, and supported upon short, thick 

 stalks. The abdomen is composed of six segments only, the telson be- 

 ing not yet clearly separated from the preceding segment. The width 

 of the abdomen suddenly diminishes at the fourth segment. The sixth 

 segment consists of a long, cylindrical piece, which terminates in a broad, 

 triangular fin. The hind border of the terminal fin is slightly convex, 

 the angles truncated and notched. It is armed with fourteen long setae, 

 which are finely feathered on both sides, excepting the outer two pairs, 

 which are feathered only on the inner side. The spaces between the 

 long setae are slightly concave, and furnished with about four very mi- 

 nute setse (PI. I. Fig. 18).* The anus lies on the lower side of the base 

 of the terminal fin, and the intestine shows through the transparent 

 shell as a slender tube passing in a direct line from the stomach to the 

 anus. 



The first pair of antennae (PL I. Fig. 15) are short, simple, composed 

 of a large basal segment followed by a small, oval, setiferous, terminal 

 segment. The distal end of the proximal segment also bears a long seta 

 on the inner side of, and longer than, the terminal segment. 



The second pair of antennae (PI. I. Fig. 16) are about as long as the 

 first pair. They are composed of a short basal segment which bears 

 two branches. The inner branch (r i), which develops into the flagellum 

 of the second pair of antennae in the adult, is a slender piece tipped with 

 a long seta. The outer branch (re), which represents the "scale," is 

 at this stage much larger than the inner, divided into segments for some 

 distance from its tip, and furnished with setae on its inner border. 



The mouth is bounded in front by a large, prominent, triangular 

 labrum (PI. I. Fig. 17, lb). The mandibles (PI. I. Fig. 17, III) are 

 slender, and taper gradually to the tips, which are armed with three 

 teeth. There is no trace of a mandibular palpus at any stage in the 

 development. 



The first pair of maxillae (PI. I. Fig 17, IV), consist of two lobes, the 

 outer of which bears a one-jointed palpus. Both lobes, as well as the 

 palpus, are furnished with setae on their borders. 



The second pair of maxillae (PI. I. Fig. 17, V; Fig. 12) are composed 

 of an inner plate, the inner edge of which is divided into five lobes, and 

 an outer plate, the scaphognathite, which lies under the carapace and 

 projects far beyond the inner plate toward the eye-stalk. All the 

 lobes are beset with setae. The scaphognathite is in constant motion, 



* The caudal fin of the first zoea-stage of Palcemon serratus is figured by P. 

 Mayer {op. cit., Jena. Zeitschr., Vol. XI. PI. XV. Fig. 49). 



