120 
Abdomen of the Mate five-jointed, the first joint trans- 
verse, arcuate, linear; the second a little longer, anteri- 
orly arcuate-produced ; third very much elongated, to-~ 
wards the apex a little narrower, the point subemargi- 
nate; fourth subquadrate, the point subemarginate; fifth 
triangular, 
THIA POLITA. 
TAB. CIII. 
T. testa convexa polita sparsé punctata; orbita posticé 
emarginata ; lateribus utrinque obscuré quadriplicatis ; 
fronte integra arcuata, , 
Cancer residuus. Herbst, iii. 53, tab. 48, fig. 1.? 
Thia polita. Leach, Trans. Linn. Soc, xi. 312. 
Habitat 
POLISHED THIA. 
Shell convex, polished, sprinkled with punctures ; orbit be- 
hind emarginate; the sides obscurely four-folded ; front 
entire, arcuated. 
This animal, unless it be cancer residuus of Herbst, ap- 
pears to be a new species. 
As a genus, Tura is very interesting; it forms one of 
three genera forming a natural group, which probably be- 
gins that order of Podophthalmous Malacostraca, to which 
it belongs. 
