320 BULLETIN OF THE 
almost every detail like that of the adult prawn, parts of which are 
represented on Plate IV. Figs. 16 — 31. The integument, however, is 
much thinner and more transparent, the legs are longer, and the exter- 
nal plate of the swimmerets is not divided by a transverse suture. The 
rostrum (Pl. IV. Fig. 32) is nearly as long as the portion of the carapace 
behind it. Viewed in profile, it increases in depth from the root to 
beyond the middle, thence tapers with a gentle upward curve to a fine 
point at the tip. It is armed above with seven, below with three, teeth. 
The second tooth, counting from the base, lies over the proximal end of 
the eye-stalks. They are all directed forward, and in the intervals bo- 
tween them are two or three hairs. 
As the prawn develops, new teeth are added between the older ones 
and the tip of the rostrum. In a specimen which measures 9 mm. 
in length, the dental formula is $ (Pl IV. Fig. 33). In the mature 
prawn the number of teeth on the rostrum is commonly nine above and 
four below (Pl. IV. Fig. 30), but is subject to great variation. Thus, I 
find on looking over a large series of specimens measuring from 28 mm. 
to 42 mm. in length, the following formulz for the rostral teeth : 
n M, M, $, 5 b $, fb $ 5, $ $ 
Hence will appear the folly of those zoölogists who have taken the form 
of the rostrum as a means for distinguishing species in the group of 
Caridea. The carapace is provided, moreover, with an antennal and a 
branchiostegal spine on the fore margin of each side. There is now no 
trace loft of the large supra-orbital spine which was so conspicuous in 
most of the larval stages. The pterygostomian angle is rounded off as 
in the full-grown individuals. The pleure of the fifth abdominal seg- 
ment extend backward over the following somite, but are not drawn out 
into a long spine as in the larval stages. 
The telson has the same form and armature as in full-grown speci- 
mens. It tapers posteriorly to a very narrow hind margin which is pro- 
duced in the middle in the form of a stout tooth. From the lower face 
of this median tooth issue a pair of long, plumose sete. On each sido 
of the median tooth is a long spine, which is articulated with the telson, 
and outside of these is a short spine, similarly articulated with the 
»xternal angle of the posterior border of the telson. The dorsal surface 
of the telson has four small spines arranged as in the mature prawn. 
The third flagellum of the first pair of antenna is now present as a 
short, two-jointed appendage tipped by fine hairs (Pl. IV. Fig. 15, r e). 
It does not issue from the peduncle of the antennule, but from the inner 
