[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 “appeared desirous 
to protect themselves by burrowing in the sand, in order to wait the 
return of the tide,” 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 a 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 itis 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, aud is probably the young of one 
of the species of Gelasimus. The carapax is 1.0™™ 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 towing-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™" in length and 0.9 to 1.0™™ in 
breadth. The front is broad, concave above between the eyes; the 
middle portion projects obliquely downward and terminates in a short, 
obtuse rostrum; while 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 
