OF THE MAKEAN SEEIES. 377 



close flie outer extremity of the petal, the outer series of pores marking a well-defined, 

 rounded, but slightly elliptical, outline at the end of the petal. The inner pores are 

 round, and the outer pores are often very slightly oval or subpyriform ; they are united 

 by a distinct, but very shallow, conjugating furrow, and the broad intermediate costae are 

 ornamented with a row of 3-5 small scrobiculated tubercles rather widely spaced, and 

 with small intervening granules in serial line. The broadest part of the poriferous 

 zone is 3-5 millim., and is very little wider than one third the interporiferous area at 

 that place. The widest part of the interporiferous area is at the same place, and 

 measures 9 millim. in the postero-lateral petals, and a trifle less in the anterior pair. 

 The odd anterior petal has a rather fuller and more rounded appearance at the 

 extremity than the others, in consequence of maintaining its greatest breadth undi- 

 minished rather further outwards than is the case in the paired petals. The distance 

 of the antero-lateral petals from the margin is rather more than half their length, and 

 that of the postero-lateral pair slightly greater ; and the distance of the odd anterior is 

 greater than that of the anterior pair, but less than that of the posterior pair. 



The interradial areas are narrow and band-like towards the apex, in consequence of 

 the size of the petals. The ornamentation of the interradia on the outer part consists 

 of very small primary scrobiculated tubercles, widely spaced, with the smallest inter- 

 spaces distinctly greater than the diameter of the scrobicules, and others not unfre- 

 quently twice as great or even more. The interspaces are ornamented with very 

 minute and very widely spaced miliary granules, which have the appearance of standing 

 on a level surface. The ornamentation of the interporiferous ai'eas is much more 

 crowded in every respect, and has consequently an altogether different facies, the 

 elements of its composition being, however, the same as those just noticed. On the 

 actinal surface the primary scrobiculated tubercles are larger along the median area of 

 the interradia, and are widely spaced there. The tubercles diminish greatly in size 

 along the margins of the deep ambulacral furrows. 



The actinal surface is subplane, and rather abruptly depressed subcentrally to form 

 a moderately deep, but not widely extending cavity, in which the peristome is situated ; 

 the interradia at the brink of the concavity having a puffed up or pulvinate appearance, 

 which is further emphasized by the deep but narrow furrows of the ambulacra. These 

 extend from the peristome up to within a very short distance from the margin ; and in 

 some examples a faint continuation may be traced up to the extreme margin. In 

 large examples the interradial plates have their transverse sutures very faintly 

 channelled for some distance from the ambulacral furrow and the surface of the plates 

 is faintly tumid — characters which, together with the small tuberculation above noticed, 

 give a very ornate appearance to the actinal surface. 



The peristome is small and subcircular, sometimes with a faint tendency to a 

 decagonal form. The periproct is small and circular, situated rather less than its own 

 diameter away from the margin. 



Variations. In general structure this species appears -to be more constant than 

 usual in the genus ; there is, however, considerable variation in the marginal contour, 

 and this, at first sight, leads to the supposition that the form is more variable as a whole 



3f 



