than that of the recent crab. The upper edge of the hand, too, of the 

 recent animal, has also some 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 exa- 

 mine 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 animal. 



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 re- 

 mains being sometimes found in a coiled, and sometimes in an extended 

 state ; as well as from the head and tail part being frequently found 

 separated, and giving room for suspicion that they might belong to dif- 

 ferent animals. From Bromel this fossil received the name of Lapis in- 

 sectiferus and Insectum vaginipenne; by Wolsterdorf, who considered it as 

 a fossil bivalve, it was called Conchitus trilobus ; by Hermann, Pectun- 

 culites trilobus bnbricatus \ by Da Costa, Pediculus marinus ; by Linnaeus, 

 Entomolithes par adorns; by Baumer, Trigonella striata; and by Wilke, 

 Entomolithus cancriformis marini. 



Mr. Martin, who, in his Petrificata Derbiensia, inquired, with consider- 

 able 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 ap- 

 pears to be very considerable differences in the forms of the fossils of this 

 kind, which have been found in different parts, it seems to be advisable, 

 until we gain further information, to form for it a temporary genus, 

 which may be named and characterized 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 agree- 



