OF WESTERN SIND. 335 



smallest specimens which we unhesitatingly refer to E. Jacguemonti are from 22-27 

 millim. in length ; there are, however, in the collection three or four other specimens, 

 smaller than this, from as many diflFerent localities, and these we are strongly inclined 

 to consider also as young forms of E. Jacguemonti. These small tests are remarkable 

 for the great tumidity of the actinal area, the profile contour of which is almost as 

 fully convex as that of the abactinal area, and in some of them at least there is no 

 depression around the peristome. This aperture is comparatively small, and the peri- 

 proct is higher in the margin in some of them than usual in the adult forms ; but there 

 appears more or less variation in the position of the periproct even amongst the small 

 forms. These characters are such as might well be regarded as youthful features, and 

 in other respects the tests do not differ more from the type form of E. Jacquemonti 

 than our knowledge of the growth-stages of recent species of Echinolampas leads us to 

 regard as perfectly consistent with the view that they are immature specimens. 



There is, however, an example measuring 32 millim. in length, which presents all 

 these extreme characters to the fullest extent ; and this form appears to accord in every 

 respect with the species named E. spheroidalis hy d'Archiac and Haime; although in 

 our opinion it is not improbable that with a larger range of small forms and in a better 

 state of preservation than those we possess, E. spheroidalis may ultimately be found to 

 be in reality only the immature stage oiE. Jacguemonti. From the fact that our largest 

 spJieroidalis-Yike specimen (32 millim.) presents the above-mentioned weU-marked 

 features — youthful though they appear — at a size much greater than that at which the 

 young E. Jacguemonti already exhibit their own specific and unmistakable habitus, we 

 refrain for the present from interfering with the specific independence of jB. spheroidalis, 

 and rank the small specimens under notice provisionally and with doubt under that 

 designation. 



Variations. This species is remarkable for its variability within certain limits ; and 

 very numerous modifications of form are to be found in the collection under notice. 

 These chiefly affect the relative proportions of length and breadth, the outline of the 

 abactinal profile, the marginal contour to some extent, and also the breadth of the 

 ambulacral petals. Considerable though these variations appear when extreme examples 

 are compared, the intermediate stages are so numerous and unmistakable that we do not 

 think it necessary or desirable to give names to these varieties ; and this the more as the 

 different changes above indicated may be found in a series of specimens from one and 

 the same locality, and apparently of similar size, age, and fossilization. 



Some forms are more elongate and distinctly ovate in marginal outline than others, 

 as given in Figs. 1 and 2. Others, again, have the anterior margin fuUer and flatter, as 

 in Figs. 3-5 ; and this, in some rare cases, is carried to such an extent that the anterior 

 margin has quite a truncate appearance, and the antero-lateral interradia present a 

 considerably tumid angularity. In other tests, again, the margin is more orbicular (see 

 Fig. 6). Considerable variation exists as to the degree of the tumidity developed in the 

 posterior column of the postero-lateral interradia, and also as to the prominence of the 

 posterior rostration. Another feature subject to much variation, and which at the same 

 time produces a very striking series of modifications, is the relative height of the abac- 



