[535] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 241 



swimming existence like true pelagic animals, until they become full- 

 grown in the megalops state. Say mentions that his specimens were 

 found cast upon the beach by the refluent tide and &quot; appeared desirous 

 to protect themselves by burrowing in the sand, in order to wait the 

 return of the tide, 77 but they were more likely awaiting the final change 

 to the terrestrial state. The tufts of peculiar hairs between the bases 

 of the second and third ambulatory legs, and, in the adult, connected 

 with the respiration, are present in the full-grown megalops. and are 

 undoubtedly provided to fit the animal for its terrestrial existence as 

 soon as it is thrown upon the shore. The young in the magalops stage 

 occur on the shore of Long Island, in August, and perhaps earlier. At 

 Fire Island Beach in 1870 no specimens of Ocypoda were discovered till 

 the last of August, and those first found were the smallest ones obtained ; 

 by the middle of September, however, they were common on the outer 

 beach, and many of them were twice as large as those first obtained. 

 Although careful search was made along the beach for several miles, 

 not & specimen of the adult or half-grown crab could be found ; every 

 individual there had evidently landed and developed during the season. 

 Probably all those living the year before had perished during the win 

 ter, and it is possible that this species never survives long enough to 

 attain its full growth, so far north. 



A small megalops, taken in the towing-nets in considerable numbers 

 at Wood s Hole on the evening of September 3, resembles in several 

 characters the megalops of Ocypoda, and is probably the young of one 

 of the species of Gelasimus. The carapax is 1.0 mm long and 0.7 

 broad. The front is narrowly triangular, deflexed perpendicularly, 

 somewhat excavated between the eyes, and terminates in a long, slen 

 der, and acute tip. The sides are high and impressed for the reception 

 of the three anterior ambulatory legs as in the megalops of Ocypoda, 

 although in the alcoholic specimens examined the legs are not closed 

 against the sides. The posterior ambulatory legs are small, and lodged 

 in grooves on the surface of the carapax, much as in the megalops of 

 Ocypoda. The external maxillipeds are very much like those of the 

 megalops of Ocypoda. 



A peculiar megalops, belonging apparently to some Grapsoid group 

 of crabs, was several times taken in the towiug-net in Vineyard Sound 

 from August 5 to September 3, on the latter date in the evening. In 

 these the carapax is 1.2 to 1.3 mm in length and 0.9 to 1.0 mm in 

 breadth. The front is broad, concave above between the eyes ; the 

 middle portion projects obliquely downward and terminates in a short, 

 obtuse rostrum ; Avhile the lateral angles project forward into a promi 

 nent tooth above each eye, so that, when seen from above, the frontal 

 margin appears transverse and tridentate, the teeth being separated by 

 considerable spaces. There are no dorsal spines or tubercles upon the 

 carapax. The sides are high, and are apparently impressed for the 

 reception of the anterior ambulatory legs. The posterior ambulatory 



