240 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [534] 
of the orbit and no dorsal spine upon the carapax. The fourth segment 
of the sternum is armed each side, just within the bases of the legs, with 
a long and broad spine projecting backward and slightly outward, as in 
Cyllene furciger. The chelipeds and ambulatory legs are long and slender, 
and the dactyli of the posterior pair of legs are expanded and lamellar, 
as in the megalops of Platyonichus. The abdomen is about as long as 
the carapax excluding the rostrum, and the fifth segment is armed with 
a stout spine each side of the postero-lateral angles. 
A very large megalops, quite different in structure from those already 
mentioned, is occasionally found thrown upon outer beaches on the 
southern coast of New England and Long Island, but is apparently much 
more common upon the coast of the Southern States. This is undoubt- 
edly the young of Ocypoda arenaria, and was long ago described by Say 
(Journal Acad. Nat. Sci., Philadelphia, vol. 1, p. 157, 1817) as Monolepis 
inermis, and it is partially figured by Dana, (Crust. U. S. Expl. Exp., 
Plate XXXI, fig. 6.) The carapax is very convex above, broader behind, 
and has no dorsal spine. The front is deflexed sharply downward and 
a little backward, and the extremity is tricuspidate, the median tooth 
being long and narrowly triangular, while the lateral teeth are small 
and obtuse. Thesides are high and impressed so as to receive the three 
anterior pairs of ambulatory legs. The third pair of ambulatory legs 
are closely appressed along the upper edge of the carapax and extend 
forward over the eyes, their dactyli being curved down over the eyes 
and along each side of the front. The posterior legs are small and 
weak, and each is folded up and hes in a groove on the latero-posterior 
surface of the carapax. The external maxillipeds have almost exactly 
the same structure as in the adult Ocypoda, and, as in the adult Ocypoda, 
there is a tuft of peculiar hairs between the bases of the second and 
third ambulatory legs. I have specimens of this megalops from Block 
Island, and have myself collected it, late in August, at Fire Island 
Beach, Long Island. In the largest specimen from the last locality the 
earapax is 6.4™™ long and 5.6™™ broad. 
A large number of young specimens of the Ocypoda, collected at Fire 
Island Beach, indicate plainly that they had only recently changed from 
this megalops. The smallest of these specimens, in which the carapax 
is 5.6 to 6.0" long and 6.1 to 6.5™™ broad, differ from the adult so 
much that they might very easily be mistaken for a different species. 
The carapax is very slightly broader than long, and very convex above. 
The front is broad, not narrowed between the bases of the ocular 
peduneles, and triangular at the extremity. The margin of the orbit is 
not transverse but inclines obliquely backward. The ambulatory legs 
are nearly naked, and those of the posterior pair are proportionately 
much smaller than in the adult. 
The adult Ocypoda is terrestrial in its habits, living in deep holes 
above high-water mark on sandy beaches, but the young in the zoéa 
state are undoubtedly deposited in the water, where they lead a free- 
