56 : ZOOLOGY. 
the other is behind it, at a distance of about an eighth of an inch. One pair of spines may be 
seen—one on each side of the postrostral—immediately above the orbit. Another pair occu- 
pies the externo-inferior angle of the orbit. Finally, a third and very small pair may be ob- 
served at the inferior and anterior angle of the carapax. 
There are nine gills on each side, disposed in a double series, in the following manner: 
The external series, composed of five of these appendages, are much the smallest ; the anterior 
one rests upon the base of the external jaw-leg ; the four remaining ones are situated immedi- 
ately above the insertion of the anterior four pairs of ambulatory legs. The gills of the inner 
series, four in number, are disposed obliquely opposite the insertion of the ambulatory legs ; 
they increase gradually in size from forwards backwards. 
The jaw-leg (external or sixth pair of mandibles) is three inches and a quarter long, stretch- 
ing beyond the apex of the rostrum for about the half of their length, and composed of five arti- 
cles. The basal is a circular ring, bearing a very small palpiform appendage, placed trans- 
versally, and directed backwards. The second article is subtriangular, very small, developed 
only upon the outer or inferior aspect of that organ, and upon its inner edge is a slender, palpi- 
form, subarticulated appendage, nearly two thirds the length of the third article, tapering, 
flattened, and provided upon its inferior edge with a series of closely-set hairs or sete. The 
third article itself is three quarters of an inch long, anteriorly subcylindrical, posteriorly con- 
cave immediately beneath the mandibles, for whose benefit this concavity exists; its antero- 
superior edge is provided with two small spines. The fourth article is small, about a quarter 
of an inch long, subcylindrical, and spineless. The fifth article measures two inches and three 
sixteenths ; it is slender, cylindrical, and tapering towards its extremity, which is provided 
with five or six minute spines. 
The mandibles of the fifth pair (proceeding from the innermost or first) are composed of five 
articles, the fifth and largest of which is flattened and bent downwards upon the fourth, which 
is the smallest. Exteriorly to the first or basal article arises a processus, bearing a amembran- 
ous palpa and a subcircular flap, above which, and from the external edge of the second article, 
may be seen, stretching forwards, a palpiform appendage about half an inch long, and exhibit- 
ing distinct traces of transverse articulations, most numerous towards its extremity, The third 
article is of moderate development. 
The fourth pair of mandibles consist of but one article each, thin, foliaceous, subtriangular, 
cochloid, provided upon the posterior portion of its base with a double, subelliptical, membranous 
expansion, and directed forwards ; a crustaceous expansion, terminating in two small, filiform 
pseudopalpz, one larger than the other. 
The third mandible is composed of a few very thin, foliaceous, and rounded pieces, broadest 
towards the mouth, and provided upon their external margins with a crustaceous expansion, 
directed forwards, besides a tapering and hairy one extending backwards across the gills. 
The second mandible consists of three small plates, two inferior, subcrustaceous, and flexible, 
whilst the third is rigid, cochloid, and provided upon its margin with a double and close series 
of very small, conical, and slender black spines. At the base and upper portion of this pair of 
mandibles may be observed a rudimentary palpa. 
The jirst or innermost mandible consists of one piece only, subcylindrical upon its base, termi- 
nating anteriorly in processi, the inner of which is stout and blunt upon its apex, whilst the 
other is cochloid, and margined with a series of small, conical, black spines. 
The upper labia is short and stoutish, flattened and rounded upon its margin. 
The external antenne are more than five inches in total length. The first article is short and 
stout; provided upon its anterior margin with a small spine, and upon its inner edge is inserted 
an elongated, sword-shaped, subtriangular appendage, anteriorly tapering to a point, and ap- 
parently composed of two elongated pieces soldered together, judging of this by the presence of 
a groove upon its external or upper surface. It is provided upon its inferior and crenated edge 
with a series of closely-set hairs or bristles. Beneath, and towards the inferior surface of the 
