488 CRUSTACEA. 



lepis, while in Marestia, they are compressed and armed with a series of 

 spines, which are prolongations of the shell, and not mere setas ; and 

 there is a striking uniformity in these spines, the third from the last 

 or outermost, being the longest, and the next either side, smaller than 

 the last. It is this uniformity which leads us to place this peculiarity 

 among the generic characters. 



The Megalopa mutica of Desmarest is not a true Megalopa, and may 

 belong to this genus. The fact that the posterior legs have not been 

 seen to overlie the carapax in that species, is not of much weight, 

 since the specimens when taken do not often have them in this posi- 

 tion ; the author had often had different species under examination, 

 before he discovered that the individuals were capable of this mode of 

 arranging the legs. There is nothing in the structure of the legs that 

 suggests this habit ; for if seen extended, as they usually are, they 

 appear like the other legs, in all their characters, excepting the long 

 setae at the extremity, which commonly are rather longer than the 

 tarsus. De Haan describes the " Megalopa mutica" as found by him 

 in Japan,* and also at the Cape of Good Hope, and it is quite probable 

 that the species was a Marestia, for no characters mentioned are at 

 variance with this conclusion ; possibly the Marestia elegans. But the 

 absence of long setae on the posterior tarsi, in the different figures of 

 the mutica, does not allow us to pronounce on an identity, while De 

 Haan says, "Specimina Japonica omnino cum Gallicis convenire 

 videntur," at the same time citing the published figures. If not a 

 Marestia, the M. mutica is the type of another genus. 



MARESTIA ELEGANS. 



Carapax antice angustus et superne visus bilobatus, pone oculos vix 

 saliens, lateribus fere parallelis. Pedes antici parvi, manu oblongd, 

 margine inferiore et superficie internet, remote hirsutis. Pedes 2>di 

 marginibm sparsim ciliati, tarso infra 7-spinoso, ad basin tuberculum 

 infra non gerente. Pedes duo postici paulo breviores, tarso infra 6-spi- 

 noso, apice unguiculato et 4 setis longis instructo. 



Carapax anteriorly narrow, and as seen from above bilobate, margin 

 behind the eyes hardly salient, sides nearly parallel and abrupt. 



* Faun. Japon. Crust., 166. 



