2/1 
asperities, which are not observable on the fossil hand. But these, he 
thinks, may possibly have been removed by friction. 
The fossil remains, Plate XVII. Fig. 11, 14, &c. which we shall 
now examine, possess so few of the appearances exhibited by any 
existing animal, as to have rendered many ingenious naturalists 
doubtful, whether they should consider them as the remains of a 
crustaceous or of a conchiferous shell. 
Various names have been given to this fossil, derived chiefly from 
the three lobular divisions by which it is so particularly marked ; but 
several appellations have also been applied to it, founded on these 
remains being sometimes found in a coiled, and sometimes in an ex- 
tended state ; as well as from the head and tail part being frequently 
found separated, and giving room for suspicion that they might 
belong to different animals. From Bromel this fossil received the 
name of Lapis insectiferus and Insectum vaginipenne ; by Wolster- 
dorf, who considered it as a fossil bivalve, it was called Conchitus 
trilohus ; by Hermann, Pectunculites trilob us imbricatus; by Da Costa, 
Pediculus marinus; by Linnaeus, Entomolithes paradoxus; by Baumer, 
Trigonella striata ; and by Wilke, Entomolithus cancriformis marini. 
Mr. Martin, who, in his Pet/ificata Derhiensia, inquired, with 
considerable success, into the nature of this fossil, concluded that the 
original of the petrified insect, found in Derbyshire, was an oniscus. 
But as we have been hitherto able to examine a part only of this 
animal, and as there appears to be very considerable differences in 
the forms of the fossils of this kind, which have been found in dif- 
ferent parts, it seems to be advisable, until we gain further informa- 
tion, to form for it a temporary genus, which may be named and cha- 
racterized Trilobites — the fossil crustaceous upper covering, oblong, 
convex, and surrounded by an entire margin : the head or thorax 
large and gibbous, with two tubercles or eyes : the back convex, formed 
of triarcuate, imbricating segments, generally agreeing in their num- 
ber with the size of the animal : the tail varying in its size and form. 
