Reprinted from the Journal of the Marine Biological Association, 
N.S., Vol. w., No. 4, March, 1897. 
Contributions to Marine Bionomics. 
By 
Walter Garstang, M.A., 
Fellow and Lecturer of Lincoln College, Oxford. 
II. The Function of Antero-lateral Denticulations of the 
Carapace in Sand-burrowing Crabs. 
THE antero-lateral margins of the carapace in many of the crabs of 
our own and of foreign coasts are beset with a row of teeth or spines, 
which vary in character and number in different species and genera. 
In the Oxyrhyncha (Spider-crabs) the whole surface of the carapace 
is generally studded with spines and stiff hairs of a peculiar character, 
but there is no general restriction of these processes of the carapace 
to the antero-lateral margins of the body. These crabs, moreover, do 
not adopt burrowing habits. Their armature of spines, tubercles, and 
hairs is employed, as is well known, for protective purposes: in some 
cases possibly as an actual defence against attack, in others (ae., 
Hurynome aspera) as a means of protective resemblance to their 
surroundings; but in the great majority as mere pegs and hooks for 
the fixation of foreign bodies, such as alge, hydroids, polyzoa, and 
ascidians, for purposes of concealment and disguise. 
In the Catometopa (Land-crabs, etc.) the carapace is usually amogth 
over its whole surface. These animals often burrow in sand, but for 
the most part their burrows are permanent subterranean tunnels and 
chambers. 
In the Cyclometopa, however—the group which includes most of our 
commoner British crabs—the back of the carapace is generally smooth, 
while the antero-lateral margins are in most forms conspicuously 
serrated. Most of these animals inhabit sandy or gravelly areas, 
and show a marked propensity towards burrowing habits. Their 
burrows are never* permanent channels or tunnels in the sand, but 
are mere temporary excavations, the sand, mud, or gravel being in 
actual contact with their bodies when imbedded. 
So far as I am aware no one has hitherto elucidated the remarkable 
constancy of antero-lateral serrations of the carapace in this group of 
crabs. I here present evidence which tends to show that the presence 
* Scylla serrata of the Natal coast appears to be exceptional in this respect. (KRAUSS, 
Die Siidafricanischen Crustaceen, 1843, p. 12.) 
