ORDER DECAPODA. 
153 
Thia, Leacli , 
Approach the last by reason of their lateral antennae,* of the 
direction of the fossets lodging the intermediate ones, of the 
form of the third articulation of the external jaw-feet, and of 
their sub-orbicular testa ; but their eyes, as well as their 
pedicles, are very small and scarcely project ; their tarsi are 
very much compressed and sub-elliptical ; the front is arched, 
rounded, and without marked denticulations. The pectoral 
space comprised between the feet is very narrow, and of the 
same width throughout ; the claws are proportionally much 
less strong ; the testa is smooth, and in some other respects 
these Crustacea approach leucosia and Corystes. The pro- 
totype species is Thia polita , Leach. 
Mursia, Leach , 
Of which but a single species is yet known, proper to that part 
of the ocean which encompasses the southern extremity of 
Africa ; it approaches Matuta and many portuni, by reason of 
the long spine with which each side of the testa is armed 
posteriorly. It also approaches the crabs, properly so called, 
in the form of the testa, and the external jaw-feet, with this 
difference, that their third articulation is in the form of an 
elongated square, narrowed and truncated obliquely at its su- 
perior extremity ; but as in Calappa and Hepatus, the hands 
are very much compressed superiorly, with a short and denti- 
culated edge. 
Hepatus, Latr 
Have, as to the widened form of their testa, the shortness of 
their lateral antennae, a great affinity with the crabs, properly 
so called, and approach Mursia and Calappa, by reason of 
