04 ' RAMBLES AND REVERIES. 



The structural details of trilobites furnish a means 

 whereby palaeontologists are enabled to arrange the 

 numerous species in well-defined groups or families. 



The AgnostidaB are eyeless and small, having 

 not more than two body-rings, the shields of the 

 head and tail being nearly equal. (Figs. 52, 53.) 



The Olenidce or Paradoxidae are characterised 

 by their long bodies, which are divided into many 

 segments. The tail-shield is small, and curved 

 spines are often found along the sides. (Fig. 51.) 



The Asaphidce are mostly made up of large oval- 

 shaped trilobites, having about eight body-rings, 

 and being covered with a smooth carapace. 



The TrimtcleidfBj containing some of the prettiest 

 of trilobites, have the head-shield large, with a 

 long process or spine hanging from each side of it. 

 (Fig. 50.) 



The Ckeiruridee consist of seven genera. The 

 number of segments is eleven, and they are free at 

 their ends. 



The Calymenidce have rough carapaces, and the 

 body usually contains thirteen segments or rings. 



Another family called Phacopidae had large 

 facetted eyes and eleven body-rings. (Fig. 16.) 



The Lickades, consisting of only one genus, have 

 small heads and a tail with a broad limb. 



The Prcetidce are interesting as embracing the 

 last of the trilobites, the Carboniferous Phillipsia 

 and Griffithsides. Although these are of small 

 size, the number of the body-rings is usually nine. 

 The carapace or body-covering of Phillipsia is 

 generally rough or granulated, and seems to have 



