Scientific Reviews. 33 
two sexes, he now adds drawings of the antennz and external feet- 
jaws, (pieds machoires, ) organs which furnish the generic charac- 
ters. Upon the sixth plate two species of Grapsi are figured, the 
turtle and the pelagic, which Latreille thinks may be the Cancer 
mutus of Linneus. The next presents the Homola Cuvieri, a species 
which, in a memoir read to the Academy of Sciences in 1815, La~ 
treille, (in establishing the same genus, under the denomination of 
Hippocarcinus,) drew from the neglect under which it had lain 
since the time of Aldrovandi. Two Leucosie, of the sub-genus 
Zlia of Dr. Leach, one of which has been named nucleus, and the 
other the rugulosa of Mr. Risso, compose the 8th plate. The Go- 
noplax Rhomboides, Latr. (Ocypede longimana, Risso,) occupies 
the ninth. The tenth and last represents, with details, the Pa- 
gurus striatus. 
In speaking of the Gonoplaces, (Rhombilles of the French wri- 
ters,) he refers to the determinations of Mr. Desmarest, who has 
figured five fossil species, (Desm. Consid. Gen. sur les Crustacés, 
p. 124. and Hist. Nat. des Crustacés fossiles, p. 99.) Gonoplax 
Latreillu, G. incisa, G. emarginata, G. impressa, G. incerta ; 
but these, according to Latreille, would belong, some to the genus 
Gelasimus, others to the genus Macropthalmus, and one to the 
genus Concropthalmus, (Annales des Sciences Naturelles, t. 17. 
p: 78.) 

A Dissertation on the Course and probable Termination of the 
Niger. By Lievut.-Gen.. Sir Rurane Donkin, G. C. H. 
K.C.B. and F.R.S. Murray, London, 1829. 
THERE are few problems in geography which present such a 
combination of interesting discussions, as the course of the Niger in 
the centre of Africa, the determination of which has been long 
held in anxious request. To ally the existing condition of the 
country with the relations of early historians,—to fix the precise 
geographical positions of mountains, rivers, and towns,—to settle 
the question as to the possibility of an immense river running across 
a continent, or of its terminating in the interior,—have alike em- 
ployed and bafiled the ingenuity of the classical antiquary, the spe- 
culations of the geographer at home, and the unwearying persis- 
tance of the traveller abroad. | 
Many attempts, however, have been made by enthusiastic and 
indefatigable men to acquire such information as would enable 
them to lay down a chart with minuteness and accuracy. But 
every evil conspires to prevent Europeans from penetrating these 
regions. The climate of that ‘ pest-house of the world,” inter- 
tropical Africa, brooding over the land with deadly influence, 
spreads universal destruction over the path of all strangers. The 
savage tribes which infest the soil, vying with the inclement ele- 
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