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 fur tiger. 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 arcnaria, and was long ago described by Say 

 (Journal Acad. Nat. Sci., Philadelphia, vol. i, p. 157, 1817) as Monolcim 

 inermis, and it is partially figured by Dana, (Crust. U. S. Expl. Exp., 

 Plate XXXI, fig. C.) 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. The sides 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 lies in a groove on the latero-posterior 

 surface of the carapax. The external niaxillipeds 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 

 carapax is 6.4 lum long and 5.6 mm 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 mm long and 6.1 to 6.5 mm 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 

 peduncles, 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 zoe'a 

 state are undoubtedly deposited in the water, where they lead a free- 



