VV. KEEPING ON TSE DISCOVERY OF MELONITES IN BRITAIN. 399 



ranges of plates, with a prominent median ridge formed by arched 

 plates which are twice as large as the others. 



M. Etheridgii is perhaps further distinguished by the size of its 

 tubercles and spines, no trace of either of these being seen in the 

 beautiful specimens of M. nudtiporus preserved in the British Museum*. 

 Although some of the plates in this Urchin articulate with each other 

 by inclined faces, yet I do not believe that its test was flexible, but 

 rigid, as is proved by the thickness of the plates and the mode of 

 preservation of the ambulacral areas ; therefore it must be classed 

 in the group of Perischoechinida tessellataf. 



I have named this species after Mr. K. Etheridge, F.R.S., and 

 take this opportunity of thanking him for that assistance which he 

 is ever ready to give. 



Locality and Formation. — Both the specimens are from the Car- 

 boniferous Limestone of Derbyshire. 



Discussion. 



Prof. Morris remarked that certainly Melonites was hitherto un- 

 known in England. The American species has 8 ambulacral and 7 

 interambulacral ranges of plates. He thought the specimen was in 

 too imperfect a state of preservation to show whether the valleys 

 described by the author as dividing the ambulacral areas really 

 existed. 



The President remarked that the presence of the spines in these 

 specimens was very interesting, as the spines of Melonites were pre- 

 viously unknown. He inquired as to the true relationships of this 

 genus, and whether it approached the Crinoids, and stated that 

 similar plates were to be met with in abundance in a separate state 

 in the Lower Carboniferous shales near Glasgow. 



Mr. Keeping stated that Mr. J. Young had mentioned to him the 

 existence of traces of Melonites in the Glasgow shales. He explained 

 further the grounds on which he assumed that the ambulacral areas 

 showed a double convexity ; and, in reply to the President, stated 

 that he regarded these Urchins as allied to the Cystoids, and men- 

 tioned that a Russian form of Caradoc age, described by Schmidt, 

 is intermediate between the Echinoids and Cystoids, the part de- 

 scribed by that author as the mouth being really the mark of a 

 stalk. 



* Prof. J. Hall kindly informs me that Melonites multiporus has no tubercles 

 or spines on the test, the plates being simply pustulose over the entire surface, 

 t Perischoechinida tessellata, as defined by me, Q. J. G. S. Feb. 1876. 



Q. J. G. S. No. 128. 2 r 



