OF THE COASTS OF SOUTH AMERICA. 53 
nished with a strong tubercle as in Mithr. verrucosus, Edw.) The remaining feet co- 
vered with similar tubercles above, and a few very small ones beneath. The nails much 
hooked and acute. 
In the young state, the carapax, the legs, and the antenne are covered with a thick 
coat of hair, and the tubercles are small and sharp, so that the margin of the shell, the 
rostrum, the orbits, and the legs, may rather be described as spinous than tuberculated. 
Colour of the adult a deep purplish brown ; of the young, light brown. 
Length of the carapax in the adult female 2 inches ; breadth 2 inches. 
Two adult females and several young specimens of both sexes were obtained by 
Mr. Cuming from sandy mud at the Gallapagos Islands at the depth of six fathoms. 
The Cancer Ursus of Herbst has not, I believe, been observed since his figure was 
published. Dr. Edwards suggests that it may be a species of Paramithraw, and the 
erroneous drawing of the anterior feet in Herbst’s figure might authorize such a suppo- 
sition. The examination, however, of several specimens of different ages has enabled 
me to ascertain that it is a true Mithraz, and that the characters of the genus are so im- 
perfectly developed in the young state, that not only in this, but in many other instances 
such a mistake might readily occur. It was from a specimen about half grown that 
Herbst’s figure was taken, and I now offer a figure of a still younger individual, and 
one of an adult female, with the assurance that the intermediate states enable me con- 
fidently to consider them as the same species. The little spines in the young are every- 
where identical with the tubercles in the adult. 
The observations which J have here ventured to make, show the importance of ex- 
amining Crustacea in various degrees of development, in order to ascertain the specific 
and even the generic characters. The parts which differ most in the two sexes, are 
generally found to be those which undergo the greatest changes by age. And in those 
genera which, like the present, exhibit a peculiar structure in the hands,—organs which 
offer the greatest variation in both these circumstances,—it is peculiarly necessary that 
the structure of these parts in both sexes and at various ages should, if possible, be 
described. 
Herbst gives his own collection as the place where the specimen he figured was de- 
posited, and states the South Sea as its habitat. 
Mirurax Noposus. 
Tab. XI. Fig. 1. 
Mithr. testd trigono-rotundatd ; margine tuberculis tribus fortibus, rotundatis, et dente 
unico ; rostro brevi ; pedipalpis articulo secundo caulis externi irregularitér lunulato ; 
manibus levibus, supra carinatis ; brachiis et carpis tuberculatis ; pedibus posterioribus 
supra spinosissimis et pilosis. 
Hab. ad Insulas Gallapagos dictas. 
Mus. Soc. Zool., Bell. 
