ENCRIN1TES. 125 



pelvis. Crotalocrinus has the first part of its name 

 derived from a Greek word signifying a " child's 

 rattle," on account of its peculiar shape and appear- 

 ance. The arms commence at the top of the body, 

 and as the joints or ossicles are fastened to each other 

 sidewise, as well as vertically, the arms have a sub- 

 division resembling the meshes of a net, or the basket- 

 work of a child's penny rattle. When portions of 

 these arms are found, as they frequently are, on the 

 surfaces of the Wenlock and Dudley limestones, they 

 look like fossil Polyzoa or " sea-mats," and are 

 frequently mistaken by young geological students for 

 such. Another Silurian genus of Encrinites, called 

 Anthocrinus from its flower-like appearance, has its 

 arms subdivided, something after the fashion of those 

 of the Crotalocrinus. 



Periechocrinns, Rhodocrinus, Taxocrinus, and Po- 

 teriocrinus are other common Silurian genera, nearly 

 always found in the various limestones of that forma- 

 tion. Rhodocrinus, or the " Rose Encrinite," ranges 

 upwards in the Primary rocks to the Carboniferous 

 limestone, in which it is found in and about Clitheroe, 

 in Lancashire. The joints of its column may be 

 known by the five-sided hole running through the 

 middle. On examining the weathered surfaces of 

 the Silurian limestones in the neighbourhood of 

 Wenlock or Dudley, the student will often find 

 splendid, sometimes perfect, specimens of one or 

 another of the above-mentioned Crinoids. Glypto- 



