528 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



an adult form, it would uudoubtedly be regarded as a distinct genus. 

 The rostrum is bifid at tip, and armed with three or four teeth on each side 

 toward the base, and in some specimens with a minute additional spine, 

 on one or both sides, close to the tip. The flagella of the antennulse ex- 

 tend scarcely beyond the tip of the rostrum. The antennal scale is very 

 much reduced in size, but is still conspicuous and furnished with long- 

 plumose hairs along the inner margin, while the flagellum is as long as 

 the carapax. The palpi of the mandibles have assumed the adult 

 character, but the mandibles themselves have not acquired the massive 

 molar character which they have in the older animal. The other month- 

 organs have nearly the adult form. The anterior legs, although quite 

 large, are still slender and just alike on the two sides, while all the 

 cephalothoracic legs retain a distinct process in place of the swimming 

 •exopodi of the larva. The lateral angles of the second to the fifth abdomi- 

 nal segments are prolonged downward into long spiniform teeth, the ap- 

 pendages of these segments are proportionately much longer than in the 

 adult, and the margins of their terminal lamellae are furnished with very 

 long plumose hairs. The lamellae of the appendages of the penultimate 

 segment are oval, and margined with long plumose hairs. The terminal 

 segment is nearly quadrangular, as wide at the extremity as at the 

 base, the posterior margin arcuate, but not extending beyond the promi- 

 nent lateral angles, and furnished with hairs like those on the margins 

 of the lamellae of the appendages of the penultimate segment. 



In color they resemble closely the adult, but the green color of the 

 back is lighter, and the yellowish markings upon the claws and body 

 are proi^ortionately larger. 



In this stage, the young lobsters swim very rapidly by means of the 

 abdominal legs, and dart backward, when disturbed, with the caudal 

 appendages, frequently jumping out of the water in this way like shrimp, 

 which their movements in the water much resemble. They appear 

 to be truly surface animals, as in the earlier stages, and were often seen 

 swimming about among other surface animals. They were frequently 

 taken from the 8th to the 28th of July, and very likely occur much 

 later. 



From the dates at which the diifereut forms were taken, it is probable 

 that they pass through all the stages here described in the course of a 

 single season. How late the young, after reaching the lobster-like 

 form, retain their free-swimming habit was not ascertained. 



The young of the different kinds of shrimp, Crangon vulgaris, Falccmo- 

 netes vulgaris, and Virhius zoster icola, when hatched from the egg, are free- 

 SNvimming animals, similar in their habits to the young of the lobster. 

 In structure, however, they are quite unlike the larva^ of the lobster, and 

 approach more the zoea stages of the crabs, which are described farther 

 on. When they first leave the egg, they are without the five pairs of 

 cephalothoracic legs, the abdomen is without appendages, and muc^h as 

 it is in the first stage of the young lobster, wliile tbe maxillipeds are 



