S. I. Smith — Early Stcifjes of the American Lobster. 371 



segments, most of which are as broad as long, and is furnished along 

 the inner side, especially on the distal portion, with many short, stout 

 and jointed sette. The terminal segment is slender, scarcely half as 

 thick as the others, much longer than broad, and obtusely rounded at 

 the tip. The inner flagellum is slender and composed of nine or ten 

 segments, which are nearly all twice as long as broad, and furnished 

 at the distal end with several very short hairs. The terminal seg- 

 ment is slightly narrower than the others, and obtusely rounded and 

 furnished with four short hairs at the tip. — In the full grown adult 

 lobster the antennuloe differ in having much longer and more slender 

 flagella, the inner being a little longer than the outer, and both extend- 

 ing for more than three-quarters of their length beyond the rostrum. 

 The outer flagellum is composed of a great number of very short 

 segments, and the terminal portion tapers to a long slender tip and 

 is furnished along the inner side with numerous set® as in the earlier 

 stasre. The inner flagellum is not so much more slender than the 

 outer as in the earlier stage, and is composed of very numerous seg- 

 ments which are as broad, or nearly as broad, as long. 



The antennte (plate XV, fig. 12, enlarged 10 diameters) still retain 

 some marked characters of the larval stage. The second segment of 

 the peduncle projects into an angle on the outside at the base of the 

 scale, not into a stout tooth as in the adult. The scale is still quite 

 large and lamelliform, projecting half its length beyond the peduncle, 

 and is furnished on the inner margin with long plumose setiB as in 

 the larval stages, though in this stage the margin projects in a slender 

 process at the insertion of each seta. The flagellum is slender, fully 

 as long as the carapax to the tip of the rostrum, and is composed of 

 thirty-six to forty segments whicli are as long as or much longer than 

 broad, and furnished at the distal end with several short hairs or 

 setje. — In the full grown adult lobster the antenna! scale is reduced 

 to a stout tooth-like appendage extending scarcely bej'ond the fourth 

 segment of the peduncle and with a thick expansion upon the inner 

 side, and the stout tooth at its base is nearly as large as the scale it- 

 self The flagellum is fully twice as long as in the young state, and 

 is composed of very numerous short segments closely articulated 

 togethei'. 



The mandibles (plate XV, fig. 19, enlarged 25 diameters, and fig. 

 20, left one seen from the inside, enlarged 40 diameters) have lost the 

 lamelliform processes and approach in general form those of the 

 adult, but the crowns are much less massive and their edges are con- 

 spicuously dentate. The palpi have the same form as in the adult, 



Trans. Connecticut Acad., Vol. II. 31 August, 1873. 



