TROPHIES FROM EGYPT 173 
dorsal shield has two long horns behind and one of porten- 
tous length in front. ven after the general appearance 
of the adult has been assumed, the young crustacean 
shows several interesting differences from its elders. The 
accompanying figure of a little one, an eighth of an inch 
long, taken off the back of its mother, exhibits a carapace 
with numerous little spines not found in the parent, and 
the telson simply ovate, instead of being subdivided by 
sutures into seven portions. Porcellana Robertsoni, Hen- 
derson, is remarkable as having been taken not in shallow 
water, but at a depth of 390 fathoms in the West Indies. 
Dr. de Man states that ‘the genus Porcellana is represented 
in the Bay of Bengal by no fewer than fifteen species.’ 
Several of them, however, as he explains, belong to the 
other genera of this family, which Dr. de Man ‘retains as 
subgenera. 
Petrolisthes, Stimpson, 1858, has the ‘ front’ undulated, 
the first joint of the second antennze remarkably short, 
not reaching the margin of the carapace, the fifth joint of 
the chelipeds often dentate on the inner margin, and the 
walking-legs as in Porcellana. Among the Crustacea 
collected on Napoleon’s celebrated Egyptian expedition, a 
species, beautifully and elaborately figured by Savigny, was 
named Porcellana Bosci by Audouin, to whom the French 
Government entrusted the task of describing the species in 
Savigny’s splendid work, in consequence of the latter 
author’s long-continued illness. This species was trans- 
ferred by Stimpson to his genus Petrolisthes, and it well 
exhibits the unusual prominence which in this family is 
often assumed by the third maxillipeds, projecting as if 
they were a powerful pair of feathered antenne. The name 
of the genus meaning ‘ rock-slider’ points to one of the 
characteristic habits of the family. 
Porcellanella (White), Stimpson, 1858, differs from 
Porcellana chiefly in having the last joint in the walking- 
legs not simple but multiunguiculate. Between these two, 
and agreeing with Porcellanella and Polyoényx, Stimpson, 
in the multiunguiculate joint, the Russian writer Czerni- 
avsky has insinuated his genus Porcellanides, 1884, in his 
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