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ECHINOBRISSUS 



ambulacrum subdepressed, recurved ; base concave ; mouth-opening surrounded by five 

 short petaloid poriferous zones. 



Dimensions. — Length seven tenths of an inch ; breadth half an inch. 



Description. — The test of this species is obtusely rounded before, and subquadrate 

 and truncated behind ; the sides are slightly compressed, and the posterior third is the 

 widest part of the ambitus. The upper surface is convex and the under surface concave, 

 and inclined upwards towards the posterior border. 



The ambulacral areas are narrowly lanceolate, and the dorsal poriferous zones slightly 

 subpetaloidal on the sides and base ; the pores are scarcely visible on the upper surface, 

 but around the mouth they form a five-rayed star of short petaloidal pores, with five oral 

 lobes between them, as in Clypeopygus. 



The apical disc is small and excentral ; four of the ovarial plates are perforated. 

 The surface is covered with scrobiculated tubercles. The mouth is situated at the 

 junction of the anterior with the middle third, and is surrounded with the short rosette 

 of pores already described ; the base is concave between the sides, and curves upwards 

 towards the anterior and posterior borders, so that the borders of the postero-lateral inter- 

 ambulacra are convex and prominent at the sides and base, and impart to this Urchin one 

 of its best diagnostic characters. The anal sulcus is short, deep, oblong, and abruptly 

 declined, and occupies the region above the posterior border of the inter-ambulacrum ; 

 the vent opens at the extreme end of the sulcus above the middle of the test. 



Affinities and Differences. — This Urchin was well figured by Goldfuss, and much 

 resembles Ecliinobrissus similis, d'Orbigny, which appears to be a large variety of 

 E. lacunosus. It resembles E. Boberti, Gras, from the Upper Neocomian, but is 

 distinguished from that form by the following characters : the anal sulcus is lower, 

 narrower, and nearer the border ; the sides are less inflated and more compressed ; and 

 the base curves more upwards posteriorly. 



Locality and Stratigrap/iical Position. — This Urchin has been long collected in 

 the Upper Greensand at Longleat, Wilts, and from the Chloritic Marl at Chardstock ; 

 the type-specimen was obtained from the Chalk-marl near Essen on the Ruhr, 

 Westphalia. 



Echinobmsstjs Morrisii, Forbes, 1849. 



Cassidulus lapis-cancri, Morris. Cat. Brit. Foss., p. 49, 1843. 

 Nucleolites Morkisii, Forbes. Mem. Geol. Surv., decade i, p. 8, 1849. 



— — Morris. Cat. Brit. Foss., 2 ed., p. 84, 1854. 



Eciiinobrissus — oVOrbigny. Pal. Franc. Ter. Cretaces, pi. 959, 1854. 



Diagnosis. — Test oblong, anterior and posterior borders obtusely rounded ; sides 



