12 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
lias a length of ten millimeters. No specimens of these stages 
occur at the surface, as the animal now is no longer a swimmer. I 
was able, however, to rear a few from the last preadolescent stage. 
These adolescent larvae were colorless, crawled actively on the 
bottom of the dish in which they were kept, darting away when 
disturbed, and though they concealed themselves in seaweed, they 
did not burrow in the sand supplied to them. They did not take 
animal food, at least while under observation, but collected and 
devoured considerable diatomaceous matter. In all movements the 
abdomen was extended and the chelicipeds were held stiffly in front, 
the “thumbs” pointing inward and the “elbow ” not flexed. The 
adult Naushonia, however, obviously carries the “elbow” slightly 
bent, the meros pressed against the carapace, the “ thumbs ” approxi¬ 
mated, and the outer margins of the propodi separated. This differ¬ 
ence between the adolescent and the adult recalls *Homarus, where 
the first adolescent — fourth — stage keeps the “elbows” of its 
chelicipeds straight, so that the apices are parallel, while the adult 
approximates the tips. 
As can be seen by reference to the figures, these stages (pi. 2, 
fig. 27) closely resemble the adult shrimp, even the inevitable dif¬ 
ferences in the proportions of the parts being unusually small. The 
carapace has a broader external notch, larger rostrum, and stronger 
supra-antennal spine. Only cervical and longitudinal grooves are 
developed. The abdomen is a third shorter in proportion to the 
carapace but is otherwise like the abdomen of the adult. The 
telson (pi. 1, fig. 18) has a spine at the external angle. The eyes 
are visible from above. The flagella of the antennulae and anten¬ 
nae are few-jointed, as is the rule among immature Decapoda. The 
antennal scale attains the base of the external spine, is smooth, and 
has the inner border finely, the outer coarsely serrate. The mandi¬ 
bles (pi. 2, fig. 28) are symmetrical and adult in form except that 
the palpus has an indistinct transverse division on the basal joint as 
if this latter represented two fused joints. The maxillae and maxil- 
lipeds (pi. 1, figs. 12, 18 ; pi. 3, fig. 42) resemble those of the adult, 
excepting the more deeply excavate base of the third maxilliped. 
The chelicipeds (pi. 1, fig. 17) are symmetrical and slender, espe¬ 
cially the outer joints. The length of the propodus is nearly four 
times the breadth, its occludent margin has three large and a num¬ 
ber of smaller teeth, and, as in the adult, is half as long as the joint. 
