ORDER DECAPODA. 153 



Thia, Leach, 



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 

 rery 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 

 ihe 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 



