174 SALENIA 



Greensand of Wiltshire. The test is small and circular ; the upper surface convex, and 

 the base flat ; the sides are inflated, and the disc conspicuous and prominent. 



The ambulacral areas are straight, with two rows of prominent homogeneous granules 

 on their margins, and oblique rows of small granulations, three in each, between every 

 pair of marginal granules (fig. 2/, 2 c). Tlie pores are unigeminaJ, the pairs slightly 

 oblique, and the zones narrow and straight. 



The inter-ambulacral areas are wide, and the two rows of primary tubercles are placed 

 close to the pores, so that the miliary zone is wide and filled with granules of different 

 sizes (fig. 2 c) ; the tubercles are of moderate dimensions, and gradually decrease from 

 above downwards. Pour of the five sides of each plate are encircled with a row of 

 mammillated granules (fig. 2f). 



The apical disc is large, solid, and prominent, the border gently undulated, and the 

 sutural lines soldered up ; in lieu thereof, there are three large punctuations between the 

 junctions of the three anterior ovarial and sur-anal plates, and between all the ocular 

 plates and ovarials ; the oviductal holes are large ; the vent is round ; the periprocte 

 thickened, prominent, and slightly excentral (fig. 2 a, 2 d). 



The mouth-opening is nearly half the diameter of the test ; the peristome is deeply 

 incised, and the lobes are nearly equal (fig. 2 b). 



Affinities and Differences. — Salenia Desori resembles S. gibba. It has, however, fewer 

 granules in the ambulacra, the inter-ambulacra are more regularly developed, the apical 

 disc is without sutures, and the mouth-opening is larger in proportion to the diameter 

 of the test. 



Locality and Strati graphical Position. — This rare Urchin was collected from the Upper 

 Greensand near Warminster. I have dedicated it to my friend Professor E. Desor, of 

 Neuchatel, one of the learned authors of the ' Catalogue raisonne des Echinides ' and 

 ' Echinologie Helvetique/ and author of the ' Synopsis des Echinides fossiles ' and many 

 other valuable works on natural science. 



Salenia gibba, Agassiz. PI. XXXIV, fig. 4 a, b, c, d, e. 



Salenia gibba, Agassiz. Monogr. des Salenies, p. 13, pi. ii, figs. 9 — 16, 1838. 



— — Agassiz et Desor. Catalog, rais. des Echinides, Ann. Sc. Nat., 3e serie, 



t. vi, p. 341, 1846. 



— — Bronn. Index Palaeontologicus, p. 1107, 1847. 



— — aVOrhigmj. Prod, de Pal. strat., t. ii, p. 180, 1850. 



— — Morris. Catalogue of British Fossils, 2nd ed., p. 89, 1856. 



— — Pictet. Traite. de Paleontologie, t. iv, p. 248, 1857. 



— — Cotteau. Paleontologie Frangaise. Terrain cretace, torn, vii, p. 151, 



pi. 1035, figs. 13—20, 1865. 



Diagnosis. — Test small, circular, upper surface inflated, gibbous, under surface flat, 



