354 ECHINOBRISSUS 



lateral ambulacra ; at this point it becomes rather abruptly truncated obliquely inwards and 

 backwards, and is again transversely truncated at the posterior border (fig. 1 b) ; the upper 

 half of the single inter-ambulacrum is smooth and undepressed (fig. 1 a) ; its lower half is 

 occupied by the wide anal valley, with its perpendicular sides and large vent, which opens 

 near the surface (fig. 1, d) ; from the sides of the valley two prominent ridges descend to 

 the border, where they form obtuse prominences, the intermediate space being truncated 

 (fig. 1 a). 



The base is undulated from the convexity of the inter-ambulacra (fig. 1 b), and the 

 depressions formed by the ambulacra as they radiate from the peristome ; the large mouth- 

 opening is situated nearer the anterior than the posterior border, in a slight depression of 

 the test ; the peristome is pentagonal, and its longest diameter is in the transverse direction 

 (fig. 1 b). The tubercles at the base are large, and disposed with considerable regularity ; 

 at the anterior margin the granules surrounding the areolas form hexagons, as shown in 

 (fig. 1 e). 



Affinities and differences. — This species is so entirely unlike any of its English 

 congeners that it cannot be mistaken for either of them, the flat, depressed upper surface, 

 the length of the test, which is rounded before and angular behind, the wide, short anal valley, 

 and large, transversely elongated mouth-opening, form a group of characters by which 

 it is separated from them. The length of the test and position of the anal valley, 

 groups it naturally with E. Goldfussii, Desor, and E. pulvinatus, Cotteau, both from the 

 " Kelloway ferrugineux " of the department of the Sarthe. It is distinguished from the first 

 by the flatness of the upper surface, and the size of the anal valley, and from the latter by 

 the absence of the tumid sides, flat dorsum, and marginal valley, which characterise the 

 French urchins. The like absence of tumidity in the sides of E. Brodiei distinguishes 

 this species from E. dimidiatus, Phil., of the Coralline Oolite. 



Locality and Stratic/rapJdcal position. — This nucleolite was collected from the Portland 

 Oolite at Brill, Buckinghamshire, by my friend, the Rev. P. B. Brodie, who has kindly 

 supplied the following note on a section of the Portland beds at that locality to accompany 

 my description of this beautiful new form : 



" The occurrence of any of the Echinodermata in the Portland Oolite is so rare, that it 

 is desirable to give a short notice of the strata at the locality whence the specimen 

 described by my friend. Dr. Wright, was obtained. The sections at Brill, in Buckingham- 

 shire, are well known from Dr. Fitton's able memoir, ' On the Strata below the Chalk,' 

 and therefore I shall content myself by a very brief account of those which came more 

 immediately under my own inspection, which are in fact identical with those given by that 

 geologist. The summit of the hill is capped by the Lower Green Sand, as stated by Dr. 

 Fitton, but as this seems to be identical with the beds above the Portland at Great Hazeley, 

 whence I procured several small Paludina similar to a species described by Professor 



