134 THE FOSSIL ECHINOIDEA. 



first inclined to place the three very small specimens from this locality as a separate 

 variety, on account of their greater rotundity and more depressed form ; but, taking 

 into consideration the great variability of the species and the scanty material, we prefer 

 to place them along with the type, recording at the same time this note. 



Illustrations of the Species in Plate XXV. 



Fig. 14. Abactinal view of the test : natural size. 



15. The same : magnified. 



16. Actinal view of the test : magnified. 



17. Longitudinal profile of the test : magnified. 



18. Transverse profile of the test : magnified. 



19. Apical disk and surrounding portions of the test : magnified. 



20. Peristome and surrounding portions of the test : magnified. 

 Variations. A large series of specimens of Echinocyamus are comprised in the 



collections from the Khirthar series, and were obtained from several localities. Con- 

 siderable variation occurs in the shape of the test, and this is found in a series of 

 specimens from the same locality, and appears to be irrespective of age or size. The 

 variation chiefly afiects the marginal contour, which may be more oval and elongate or 

 more circular than the type form ; and the test may also be more depressed and less 

 subconoid in its dorsal convexity. In fact the species seems to be as protean in its 

 form as the living representative ; and it can readily be understood that a collector, 

 having only a few specimens at his disposal, might be led to consider that he was' dealing 

 with several species if form alone were his guide. 



The following variations, each from different localities, appear to us to be worthy 

 of more than passing mention ; and although in some instances the number of 

 examples is only small, they seem to be well marked and characteristic. Even in these 

 cases, however, it is not without hesitatioit that we rank them as nominal varieties, 

 after the experience above recorded ; for the number of specimens is not sufficient to 

 thoroughly gauge the value of the variations. In our present state of knowledge we 

 are disposed to consider that they present a locational character — an opinion, however, 

 which can only be off'ered with reserve until a larger quantity of material • is available 

 for study from each locality ; for it is unquestionable that amongst a large series of the 

 normal or typical form there appear to be near approaches to the varietal forms ; whilst 

 similar approximations to the type form are found to exist, in more than one instance, 

 where a tolerable series of the variety is available. 



2. EcHiNOCYAMUS NUMMULiTicus, var. OBEsus. Plate XXV, Figs. 21-24. 



The contour of the margin is more regularly ovoid. The test is relatively much 

 higher, the longitudinal profile is more regularly arched, and the sides are more tumid 

 and rounded off imperceptibly on to the actinal surface. The examples of this variety 

 are all small, the length of the largest being 7 millim., and that of the smallest 

 4 millim. In similar sized specimens of the type form of the species the test is much 

 more depressed and fiatter than in the large and fully grown specimens ; whilst in the 

 variety under notice these characters are reversed. 



