S. J. Smith — Early Stages of the American Lobster. 3T7 



wanting, as are also the abdominal legs, while the two anterior pairs 

 of maxillipeds, or all of thera, are developed into locomotive or- 

 gans,* In no period of their development do they have all the deca- 

 podal legs furnished Avith natatory exopodal branches. There are 

 undoubtedly larval forms closely allied to those of Ifoinariis in 

 some of the groups of macrourans, although they appear to be as yet 

 unknown. 



Notwithstanding these larval forms of the lobster seen to have no 

 close affinities with the known larvae of other genera of macrourans, 

 they do show in many characters a very remarkable and interesting 

 approach to the adult Schizopoda, particularly to the Mysidse. This 

 appears to me to furnish additional evidence that the Schizopods are 

 only degraded macrourans much more closely allied to the Sergestidge 

 than to the Squill oidea. 



* The following short description of the young of Palcemonetes vulgaris (the common 

 prawn or transparent shrimp of the southern coast of New England) soon after hatch- 

 ing and when about 3'"°' long, will serve as an example of a common form of the 

 earlj' stage of the larvse in these families : The cephalothorax is short and broad with 

 a slender spiniform rostrum in front, an enormous compound eye each side at the an- 

 terior margin, and a small simple eye in the middle of the carapax. The antennulae 

 are quite rudimentary, being short and thick appendages projecting a little way in 

 front of the head ; the peduncle bears at its extremity a very short obtuse segment 

 representing the primary flagellum, and inside, at the base of this, a much longer 

 plumose seta. The antennte are slightly longer than the antennulte ; the short pedun- 

 cle bears a stout appendage, corresponding to the antennal scale, the terminal portion 

 of which is articulated and furnished with long plumose setfe, and on the inside at the 

 base of the scale, a slender process corresponding to the flagellum, terminated by a 

 long plumose seta. The first and second pairs of maxillae are well formed and ap- 

 proach those of the adult. The three pairs of maxillipeds are all developed into 

 powerful locomotive appendages ; the inner branches, or endognathi, being slender 

 pedif orm appendages terminated by long spines, while the outer branches, or exognathi, 

 are long swimming appendages like the swimming branches of the legs of the young 

 lobsters in the first stage. Both branches of the first maxillipeds are considerably 

 shorter than those of the following pairs, but otherwise like them, and the inner 

 branch of the second pair is somewhat shorter than that of the third, but its outer 

 branch is about as long as that of the third pair. The five pairs of cephalothoracic 

 legs are wanting, or only represented by a cluster of minute sack -like processes Just 

 behind the outer maxillipeds. The abdomen is long and slender, wholly without ap- 

 pendages beneath, and the last segment is expanded into a short and very broad 

 caudal lamina, tlie posterior margin of which is truncate with the lateral angles 

 rounded ; these angles each bear three, and the posterior margin itself eight more 

 stout plumose setse, the setae of the posterior margin being longer than those upon the 

 angles, and separated by broader spaces in which the margin is armed with numerous 

 very small seta3. They arrive at the adult form before they are more than 5""" long. 



