FROM THE UPPER GREENSAND. 287 



the matrix fortunately produces a very sharp cast of the interior, and as the shell was 

 very thin the outline of its structure is very well preserved. 



The ambulacral pairs form quite a " crux Andrese " on the convex surface of the highly 

 inclined dorsal surface. They were lodged in very shallow depressions, and pass nearly 

 straight out from the summit to the ambitus. The anterior pair are lanceolate and 

 moderately long, and the posterior pair short, extending half the distance between the 

 disc and the border. The poriferous zones in both pairs are nearly equal. The single 

 ambulacrum lies in a shallow anteal sinus, which scarcely grooves the anterior border. 



The ambulacral summit is extremely excentral, the disc being near the junction 

 of the posterior with the middle third. 



The upper surface is convex and very much inclined. The posterior third is the 

 highest, and the two anterior thirds slope sharply down to the border forming an angle 

 of 20°. 



The anterior border is thin, the sides inflated, and bevelled away towards the base 

 and posterior border, which is truncated concavely, and has a portion of the upper 

 surface overhanging it above. In this beak-like projection the vent is situated. The 

 periprocte is oval, the upper end reaching near to the border. 



The base is flat. The mouth-opening is situated near the border, and the peristome 

 is narrow and transversely oval ; the plastron is a little convex near the border. 



Affinities and Differences. — This species resembles E, Benevieri in its cordiform 

 outline and highly inclined upper surface. It difi"ers, however, in the shallowness 

 of its ambulacrum and in the absence of depressions for the petaloidal ambulacra, which 

 are straight in E. Quenstedtii and flexed in E. Benevieri. 



Locality and StratiffrajiMcal Position. — The only two specimens I have obtained 

 were collected from the fine marly micaceous beds of the Upper Greensand of Wiltshire. 



I have dedicated this species to Professor Aug. Quenstedt, of Tiibingen, whose 

 magnificent works on the Cephalopoda, Echinodermata, and ' der Jura ' of Wiirtemburg 

 have so greatly advanced the palaeontology of the Jurassic Formations. 



