14 THE TERTIAEY FOSSIL ECHINOIDEA 



The margin is slightly gibbose, and the ambulacra are very faintly projecting above 

 the level of the test. The ambulacra are subequal and the poriferous zones are w«ll 

 developed. 



The peristome is oblique, broader than long, and has a greater curve to its posterior 

 than to its anterior margin. The periproct is pyriform, elongate, larger than the peri- 

 stome, and its anterior end is nearer the peristome than the posterior is to the margin 

 of the test. The distance of the periproct from the posterior margin of the test is equal 

 to half its length. 



The dimensions are as follows : — Length 83 millim. ; breadth 82 millim. ; height 

 34 millim. The length and breadth may be taken as equal, and the relation of length 

 to height is 1 : 0-409. 



The flat and depressed shape resembles that of Amhlypygus dilatatus, the relation 

 of whose length to height is 1 : 0"43. 



De Loriol described Amblypygus dilatatus, Agass., in his 'Monographie des 

 Echinides contenus dans les couches Nummulitiques de I'Egypte,' 1881, as follows : — 



The shape is circular and as broad as long. The upper part is slightly swollen, 

 uniformly convex, and slightly conical at the apex, which is rather eccentric in front. 

 The actinal surface is tumid (" pulvinee," swollen like a pillow around the impression of 

 one's head) and sunken around the peristome. The margins are rounded and thick. 



The apical disk corresponds with the culminating point of the upper surface. 



The ambulacra are flush with the test, broad and very long, reaching close to the 

 edge (worn considerably in the specimen). The poriferous zones are relatively broad, 

 equalling about half the breadth of the interporiferous area. The ambulacra continue 

 on to the actinal surface as very small pores, which are in a slight linear depression 

 reaching the peristome. The peristome is very sunken, oblique, tolerably large, and has 

 the shape of an irregular pentagon with very unequal sides. The periproct is not 

 visible. The tubercles (only visible below) are very small, wide apart, and are separated 

 by numerous granules. 



The length of the specimen is 72 millim. ; the breadth is the same, and the 

 relation of length to height 1 : 0*43 



The illustration on plate iii. of his work, fig. 2 a, b, c, is of a specimen whose 

 abactinal surface has been much denuded ; moreover the area behind the peristome is 

 missing. 



The shape of the peristome is preserved, and it corresponds with that of the species 

 from Kachh. 



De Loriol makes some most important remarks on the specimens of this widely 

 distributed species. He asserts that specimens from the Vicentin are nearly as high as 

 the Egyptian form, and that one from Yberg is much flatter. He refers to Amblypygus 

 ajpheles, and does not comprehend Sismonda's figure of it, which has a small pentagonal 

 peristome surrounded by bourrelets. Evidently De Loriol is disinclined to admit 

 the species. With regard to Amblypygus Arnoldi, Desor, he says it has a high abactinal 

 surface, a thicker margin, and a less pulvinee actinal surface and smaller peristome than 

 Amblypygus dilatatus. 



