MEGALOPIDEA. 49^ 



four-lobed, the lobes subequal ; sides posteriorly not diverging, near 

 middle a single tooth. Anterior feet very stout, hand large and 

 tumid. Posterior tarsi spinous below, and having three setae at tip. 



Plate 31, fig. 4, animal, enlarged eight diameters. 



Pacific Ocean, six miles from Hall's Island, one of the Kingsmill 

 Group. Collected one specimen at 4 A. m., April 14, 1841. 



Length, two lines. Colour, strawberry-red ; legs, same colour, but 

 paler ; antennas, not coloured. Front a little narrower than the pos- 

 terior margin, and nearly straight. Body and legs short hairy. The 

 very stout hands and the tooth on the side of the carapax, as well as 

 its general form, give this species a peculiar aspect. It has, however, 

 the outer antennae and posterior tarsi of the other species. The cara- 

 pax is truncate behind, and rather narrower there than directly behind 

 the eyes. 



Genus MONOLEPIS, Say. 



We have seen specimens of but two species of this genus, that of 

 Say, the M. inermis, and another from the East Indies, collected 

 by the author. These agree in many points. 



The carapax is broadest behind, and narrows gradually forward, 

 and in front, its width between the eyes is about half the width pos- 

 teriorly. The form is very obese, and nearly straight in front. The 

 beak is flexed downward and a little backward, and its surface is but 

 faintly sulcate at middle ; the extremity is tricuspidate, the medial 

 point nearly an equilateral triangle, the others much shorter and hardly 

 acute. The sides are high and vertical, and are impressed obliquely 

 for the second, third, and fourth pairs of legs; while each leg of the 

 fifth pair when folded up, lies in a rather abrupt fossa upon the latero- 

 posterior surface of the carapax. The upper surface of the carapax, 

 in each species, has the outline and most of the markings in fig. 5 b. 

 The eyes are large and somewhat oblique. Between the buccal area 

 and the sternal fossa there is a prominence, with the surface around 

 depressed. The sternal plates project in a subacute edge, as a border 

 to the sternal fossa. The orbit is large ; but the eyes are not retrac- 

 tile; there is a break in the margin below, where the base of the 



