366 /S. I. /Smith — Early Stages of the Ainerican Lobster. 



has begun to lose its schizopodal characters and to assume some of 

 the features of the adult. 



The carapax has nearly the same general form as in the earlier 

 stages, but the cervical suture is much more distinct, and the inferior 

 angle of the anterior margin is jn-olonged into a much less prominent 

 tooth. The rostrum (plate XV, fig. 3, enlarged 10 diameters) is 

 somewhat depressed from the base to near the tip, is proportionally 

 shorter and broader than in either of the earlier stages, and its mar- 

 gins are armed with the same variable number of teeth as in the 

 second stage. 



The ocular peduncles are slightly more slender, the eyes themselves 

 are proportionally a little smaller than in the second stage, and the 

 peduncles apparently admit of considerable motion. 



The antennuljB (plate XV, fig. 9, enlarged 20 diameters) are longer 

 and more slender than in the second stage, but are still considerably 

 shorter than the rostrum. The outer flagellum is distinctly divided 

 into about ten equal segments, and the distal half of the inner margin 

 is furnished with numerous hairs similar to those in the second stage, 

 only smaller and not more than half as long. The inner flagellum is 

 three-fourths as long as the outer, slender, rather indistinctly divided 

 into eight to ten segments, and entirely naked. 



The antenniB retain the essential features of the earlier stages. The 

 scale is proportionally as large, and is furnished with the same form 

 of plumose hairs along the inner margin as in the first and second 

 stages. The flagellum is about a half longer than the scale, indis- 

 tinctly multiarticulate and apparently without terminal setae or 

 lateral hairs. 



The mandibles (plate XV, fig. 15, enlarged 25 diameters, and figs. 

 16, 17, 18) have nearly the same form as in the first and second stages, 

 but the crowns are more indurated and thickened, the teeth not quite 

 as acute, and the anterior portion of the margin not quite as abruptly 

 recurved, while the palpi have increased considerably in size, the last 

 segment being much longer than either of the others, and tipped with 

 five, instead of two, short hairs or setae. 



In the first maxilla3, the spines and seta3 upon the lobes of the 

 endognathus are more numerous and considerably stouter than in the 

 second stage. The exognathus is proportionally no longer than in 

 the first and second stages, and has the same number of setse at the 

 extremity as in the second stage ; these setae (plate XVI, fig. 2, en- 

 larged 100 diameters) are, however, proportionally a little shorter and 

 stouter, the inner, and longer, of the three terminal ones is a little 



