260 Dr. T. Wright on the Cidaridse of the Oolites. 



Locality and stratigraphical range. — This species was collected 

 by Mr. Lycett from the planking beds of the Great Oolite at 

 Minchinhampton, and we have received several specimens from 

 the same stratum at Kiddington (Oxfordshire). 



Hemicidaris pustulosa, Forbes. 



Memoir of Palaeontograph. Soc, Forbes, plate A. fig. 8, Great Oolite 

 Fossils. 



We have not seen Hemicidaris pustulosa figured by Professor 

 Forbes in the above memoir; its nearest ally, it is stated, "is 

 Hemicidaris diademata, Agass., which it resembles in the sudden 

 diminution and very small size of the uppermost interambulacral 

 tubercles, but differs in having the sutural granulated space of 

 the interambulacral areas very wide*." 



The SALENiANsf, Gray. 



This group is composed of small Urchins resembling Hemici- 

 daris ; they are distinguished from that genus, however, by the 

 number, structure, and mode of arrangement of the plates form- 

 ing the apical disc, which is composed of five ovarial, five ocular, 

 and a supra-anal plate. The ambulacral arese are narrow, carry- 

 ing secondary tubercles like Hemicidaris. The pores are dis- 

 posed in distinct poriferous avenues in single pairs. The inter- 

 ambulacral areas are wide, and their plates support primary 

 tubercles raised on mammillary eminences. We divide the Sale- 

 nians into two groups : — 



In the first group the tubercles are not perforated ; they form 

 the genera Salenia, Peltastes, and Goniophorus, which are limited 

 to the rocks of the Cretaceous period. 



In the second group the tubercles are perforated, forming the 

 genus Acrosalenia, the species of which are distributed throughout 

 the Jurassic strata. 



Genus Acrosalenia, Agass. 



Test small, more or less depressed ; anal pole surrounded by a 

 well-developed circular disc, composed of five ovarial and five 

 ocular plates, with a central supra-anal plate, composed of one or 

 more elements. The anal opening is situated at one side of the 

 supra-anal plate, and is therefore eccentrical. The ambulacral 

 areae are narrow, and support a double row of from ten to twelve 

 small perforated tubercles set on crenulated mammas. 



* Memoirs of Geological Survey, Prof. Forbes, Decade 3. 



f The group of Salenians is composed of five genera : Salenia, Gray ; 

 Peltastes, Agass. ; Goniophorus, Agass. ; Acrosalenia, Agass. ; Goniopygus, 

 Agass. 



