380 CLASS CRUSTACEA. 



or lobes, and from thence the origin of the denomination 

 trilobites. With some scientific men, these are called e7ito- 

 mosiracites. The squillae, various amphipod and isopod 

 Crustacea, have also several of their segments divided into 

 three, by two sunk and longitudinal lines ; but those lines are 

 more approached to the edges, and do not form deep furrows. 



It would seem that in many trilobites, and particularly in 

 the Asaphi, that the body is composed, (the buckler not com- 

 prehended) of a dozen segments, very much detached over 

 the sides, and of another forming the post-abdomen, or a tail, 

 triangular or semi-lunar, presenting only superficial divisions, 

 and which do not cut its edges. In the paradoxides, on the 

 contrary, the lateral lobes are terminated by sharp and very 

 distinct elongations, of which we reckon nearly twenty-two. 

 A species of trilobite mentioned by Count Razoumowsky, in 

 a memoir on the fossils, and which he presumes ought to con- 

 stitute a new genus, is, in this particidar, very remarkable. 

 Its lateral lobes form sorts of strips, very long, and going into 

 a point. The feet of the nymphs of the gnats are in the form 

 of elongated, flatted laminae, without articulations, terminated 

 by filaments, and folded back upon the sides. They are in a 

 rudimentary state, and may be analogous to the lateral divi- 

 sion of this species of trilobite, which is neighbouring to the 

 paradoxides. 



The genus Agnostus, Brogn., is the only one whose body 

 is semi-circular or reniform. In all the other genera it is oval 

 or elliptic, and presents the general characters which we have 

 above indicated. 



Calymene, Brogn., is distinguished from all the other 

 trilobites, by the faculty of being able to contract the body 

 into a ball, and in the same manner as spheroma, the arma- 

 dillo, the glomeris, that is, by ajiproximating together, un- 

 demeathj the two extremities of the body. The buckler, as 



