Remarks on the Trilobite. 27 
In further illustration of this subject, we here add, with some 
slight alterations, from Dr. Buckland’s admirable Bridgewater 
~ treatise, a considerable part of his section on the trilobites, which. 
exhibits in a very condensed form the facts and opinions which 
have any bearing on this inquiry. I have greater satisfaction and 
more confidence in referring to his remarks, than in attempting 
to offer any thing of a similar nature drawn up by myself. After 
mentioning that the serolis is the nearest approach among living 
animals to the external form of trilobites, he adds, the next “ap- 
proximation to the character of trilobites occurs in the limulus or 
king crab,* a genus now most abundant in the seas of warm cli- 
mates, chiefly in those of India, and of the coasts of America. 
The history of this genus is important, on account of its relation 
both to the existing and extinct forms of crustaceans ; in it there 
are but slight traces of antenne, and the shield which covers the 
anterior portion of the body, is expanded entirely over a series of 
crustaceous legs. Beneath the second, or abdominal portion of 
the shell, is placed a series of thin, horny, transverse plates, sup- 
porting the fibres of the branchi, and at the same time acting as 
paddles for swimming. The same disposition of laminated bran- 
chie is found also in the serolis. Thus while the serolis presents 
a union of antenne and crustaceous legs, with soft es bear- 
ing the branchise, we have in the limulus a similar disposition of 
legs and paddles, and only slight traces of antenne ; in the bran- 
chipus we find antennz, but no crustaceous legs ; while the tri- 
lobite being without antenne and having all its legs represented 
by soft paddles, is by the latter condition placed near branchipus 
*In my boyhood I was very familiar with the habits of this crustacean, called in 
the northern States, horse fish—or horse shoe fish, from its form. 
8teat, since a large individual female, (the horizontal diameter of whose shell 
might have been nine or ten inches,) afforded several gills of spawn. The habit 
of these animals is t come in with the rising tide, and to walk on the bottom, as- 
seizing the spike or tail, their motion being too slow to admit of their escape. 
Hundreds of them might have been caught at a single tide, of every size from 
nearly a foot in diameter to an inch or less—these infants having also the power of 
travelling on the bottom.—Sin. Ep. ye 
