1882. ] CRUSTACEANS FROM MAURITIUS. 543 
chitinous and membranaceous portions of this segment, situate one 
in the median line and one on each lateral margin; the lateral mar- 
gins of the second to sixth postabdominal segments are divided into 
several somewhat triangulate lobes or teeth. The eyes are short, 
and in a dorsal view are completely contained within the orbits ; the 
antennules are short, and terminate in two flagella, whereof one is 
- much thicker than the other. The large leaf-like external processes 
of the antepenultimate joints of the antennze terminate in a small 
spine at their antero-external angles, behind which are two teeth 
on their outer margins, and have a small tuberculiform tooth on 
their inner margins; the terminal antennal joints are somewhat 
obtusely angulated at the distal extremity, and have their margins 
minutely crenulated or serrated; the outer maxillipedes are small, 
with the ischium as long as the merus joints. The legs are short, 
concealed beneath the carapace, with the margins of the joints angu- 
lated ; the dactyli of all are strong, slightly curved and acute; the 
antepenultimate joints have a short spine at the distal ends of their 
upper margins ; the coxal joints of the fifth legs bear a strong spine. 
Colour (of dried exwvie) reddish-yellow,with darker reddish mark- 
ings on the sides of the branchial regions of the carapace and of the 
postabdomen, on the inner margins of the antepenultimate joints of the 
antenne and of the legs. Length of the body about 1 inch 3 lines 
(32 wmm.), greatest breadth about 83 lines (18 mm.). 
Three cast shells are in the collection. 
From the Mediterranean Pseudibacus veranyi, Guérin', this species 
is distinguished by the very different tuberculation of the carapace, 
and the emargination of its lateral margins, the closed median fissure 
of the rostrum, &c. These characters will also suffice to distinguish 
our species from the Californian form described by Prof. S. I. 
Smith? as Evibacus princeps, but which I think can scarcely be gene- 
rically distinct from Pseudibacus. P. pfeffert is most nearly allied to 
an Atlantic species described by Dr. G. Pfetfer in his memoir already 
referred to? as Pseudibacus gerstaeckeri, which, however (as it 
would appear from the description), has the carinze of the carapace 
differently disposed, and has no median depression on the cardiac 
region, but in place thereof a continuous median keel ; moreover no 
mention is made of any spines at the distal ends of the antepenul- 
timate joints of the ambulatory legs. I must therefore consider our 
species distinct from P. gerstaeckeri ; and [I have much pleasure 
in associating with it the name of the author of that important 
memoir, which is of much value to the student of the classification 
of this group. 
EXPLANATION OF PLATE XXXVI. 
Fig. 1. Palinurus longimanus, var. mawritianus (p. 540) male adult, nat. size. 
2. Pseudibacus pfefferi, p. 542, x13 diam. 
3. Inferior view of the same, X13 diam. 
1 Rey. et Mag. de Zoologie, vii. pp. 139, 140, pl. v. (1855). 
2 Amer. Journ. Sci. and Arts, xii. p. 118 (1866). 
3 Verhandl. naturwissensch, Vereins Hamburg-Altona, p. 51 (1881). 
