14 THE FOSSIL ECHINOIDEA 



little elongate, oblique groove, — the interporiferous area (or, more correctly here, the 

 ambulacral area) expanding from the petal up to the ambitus, and from thence con- 

 tracting until near the phyllode, when it again expands. The phyllode is well developed, 

 widening moderately and then contracting with a graceful curve as it approaches the 

 margin of the peristome. The plates are short and broad, and the pores consequently 

 closely placed. The pores are rather large, sunken in little cavities, punctured between 

 the sutures of two neighbouring plates, all uniformly distant from the outer extremities 

 of the plates. A double series of inner, supplemental pores, 7 to 10 in number, are 

 present within the phyllode, each pore borne on the margin of a small supplementary 

 plate inserted between the regular series of ambulacral plates which constitute the 

 phyllode. These supplementary plates are not more than half the breadth of the 

 primary ones, excepting the outermost of the series, which usually extends the whole 

 breadth of the ambulacral column. Two, or even three, primary plates stand between 

 each secondary or supplementary ; consequently the inner pores are much wider apart 

 than the outer series. The inner pores are placed in two straight lines, which 

 diverge slightly, being closer together adorally than aborally. The punctures of the 

 peristomial ambulacral plates are large and placed close together within the actual 

 margin of the peristome ; they are separated only by a broad dissepiment ; and a narrow 

 bridge-like strip forms a sharp although diminutive ridge arching over them above 

 and dividing them from the inner pores of the phyllode just described. Immediately 

 above, i. e. aboral to, this ridge are several blind pits, not punctured, which are probably 

 the cavities in which sphseridia were placed, and which, on cursory examination, are at 

 first sight rather liable to be confused with the inner pores of the phyllode. The 

 ornamentation of the interporiferous area, within the petal, is precisely similar to 

 that of the interambulacral area, and consists of minute primary tubercles, perforate 

 and crenulate (the latter quite microscopic), situated within a deep and moderately wide 

 scrobicule. The margin of the scrobicule is composed of small, closely placed, uniform 

 miliaries, forming a complete circle which comes close up to those of the neighbouring 

 primaries, any interspaces being filled up with miliaries. The whole miliary granu- 

 lation is compact and confluent, forming a uniform test-surface level with the tops of 

 the primary tubercles. Near the ambitus the tubercles are slightly smaller and more 

 crowded, the miliary interspaces being much reduced, and consisting only of single 

 lines of miliaries, which are also more completely coalesced. Towards the actinostome 

 the primary tubercles are more widely separate; but on the rest of the test the 

 ornamentation is remarkably uniform and closely crowded. 



The peristome is considerably excentric in front, moderately large, elongate trans- 

 versely, and pentagonal, the amount of angularity varying considerably. The actual 

 margin is very deep, plunging upwards nearly vertically. The interradial peristomial 

 plates form well-developed bourrelets, which are large, broad, more or less bombous, 

 and with a crested rim, the whole peristomial ring being granulated with a minute 

 tuberculation, becoming very much smaller on the ambulacral than on the interradial 

 plates. The periproct is moderately large, oval, with the elongation vertical, placed at 

 the extreme upper portion of the posterior end of the test, the upper extremity of the 



