REPORT ON THE CRUSTACEA MACRURA. 



401 



telson bears to the lateral appendages, which are thickly fringed with long, simple 

 hairs. 



On the passage from the Admiralty Islands to Japan, a small specimen was taken 

 that has features suggestive of specific difference, but considered in conjunction with its 

 small size — it is scarcely more than one-eighth of an inch in length — I am inclined to 

 believe it to be only a stage in the progressive growth of the animal. 



The carapace in this specimen is about one-third of the length of the animal. The 

 cervix is about half the length of the carapace. Rostrum sharp-pointed and obliquely 

 projecting upwards and forwards. I can detect no tooth on the frontodateral margin, 

 but a stout and short one exists above the epistoma on each side. 



From this stage the young animal rapidly assumes the permanent appearance of 

 the adult, and even so early that specimens which have only attained the length of 

 about 5 mm. possess features that demonstrate their sexual 

 condition. 



On PL LXXXII. fig. 1, a young specimen (6 mm. long) is 

 represented, which was taken in the tropical part of the 

 Atlantic in the month of April, and which is evidently an 

 immature male, for the petasma, an organ peculiar to the male, 

 exists in a saccular or bud-like form, conspicuously visible on 

 the first pair of pleopoda. In other respects the animal 

 possesses the external appearance of the female, inasmuch as 

 the two strong blunt teeth, conspicuous on the lateral margins 

 of the sixth somite of the pleon in the adult males, are 

 absent, and a feeble point near the posterior angle of the FlG - 70 -~ '> sb:th pleopod ; z - telson - 

 same somite, which is common to females of both the known species, is alone present. 



The pereiopoda are as yet in a simple condition ; the small dactylos at the extremity 

 of the posterior pah, which gives a minutely chelate character to the appendages in the 

 adult, is wanting. The telson also does not possess the large protuberance on the under 

 surface near the posterior extremity that is apparent in the fully adult male animal, but 

 is smooth and even as in the adult female. 



On PI. LXXXII. fig. 2 represents a specimen about 7 mm. in length, that was taken 

 with several others in which similar features in an incipient condition are present, and 

 the telson is smooth and without any sign of the future protuberance of the adult male, 

 but there are two small teeth, of which the anterior is the larger, on the posterior part of 

 the lateral margin of the sixth somite of the pleon. 



On PI. LXXXII. fig. 3 represents a specimen that was taken in the tropical part of 

 the Atlantic ; it is about 8 mm. in length, and in most details corresponds closely with 

 the preceding forms, excepting that it is rather more advanced in development ; 



