128 PBOF, p. M. dfncan's revision op the 



stomial membrane with its numerous plates. Practically tlie sub- 

 genus is of no great value *. 



Grenus Stirechinus, Desor, 1858, Synopsis, p. 131. 



Test tall, circular at the tumid ambitus, subconical dorsally, flat 

 actinally. 



Apical system ? 



Ambulacra moderately broad, with high compound plates ; the 

 pairs of pores in arcs of triplets, the adoral plate of the com- 

 pound a large primary, the median plate a demi-plate, and the 

 aboral a low oblique primary plate. Two vertical rows of imper- 

 forate, plain, primary tubercles, large, and each situated upon a 

 rising of the plate, so as to give a keeled appearance to the ambu- 

 lacrum beneath the bases of the tubercles. 



Interradia with two vertical rows of tubercles resembling those 

 of the ambulacra, and situated on raised keel-like projections. 

 Sutures distinct. Yariable rows of secondary tubercles and 

 miliarias. 



Fossil. Pliocene : Europe. 



Genus GrLTPTECHiisrus, Be Loriol, 1873, Ecli. Cret. de la Suisse, 

 Pal. Suisse, les Oicrsins, pt. ii. p. 169, pi. xi. 



Test small, circular in outline, tall, subcorneal or subhemisphe- 

 rical dorsally, flat actinally. 



Apical system wanting. 



Ambulacra straight, moderately broad ; the poriferous zones 

 with the pairs of pores in arcs or triple oblique series ; the plates 

 compound, as in Echinus ; the interporiferous areas with two 

 vertical rows of plain tubercles, placed near the poriferous zones ; 

 some secondaries at the ambitus, and granular throughout. 



Interradia depressed aloug the median sutures, with two ver- 

 tical rows of plain tubercles resembling those of the ambulacra ; 

 each row is on a raised vertical keel, situated in the middle of the 

 plates ; several rows of secondary tubercles. The transverse 

 sutures of the interradial coronal plates, which are moderately 

 numerous, grooved decidedly. 



Fossil. Cretaceous : Europe. 



The alliance of this genus is with the Tertiary Stirechinus. 



* On p. 91 it was noticed that Micropsis Vidali, Gott., was a Fsammechinus 

 with crenulate and perforate primary tubercles. This carries the subgenus back 

 in time considerably. 



