MICROCYPHUS MACULATUS. 467 



tubercles are of uniform size, large, occupying the whole ambulacral space, 

 with sharp, triangular pits along the median junction of the plates. The 

 inner row of pores is separated from the outer by a vertical row of primary 

 tubercles. The outer row of pores is somewhat sunken. The actinostome 

 is large, only slightly decagonal, nearly circular. The general color of the 

 test is greenish-yellow, with bright violet bare sutural areas. 



In specimens measuring 29 mm in diameter the outline is much more pen- 

 tagonal, the median interambulacral line quite re-entering ; the tuberculiferous 

 part of the interambulacral plates is reduced to an irregularly rectangular 

 space, leaving broad bare bands along the median line, connected with the 

 bare sutural spaces of horizontal sutures extending to the poriferous zone. 

 The bare median space reaches nearly to the actinostome. The tuberculiferous 

 portion of the ambulacral area is not different from the preceding stage ; 

 the poriferous zone is somewhat narrower. The anal system is small ; the 

 genital ring broad ; the genital openings large, deeply cut out of extremity 

 of the genital plates ; abactinal system prominent ; genital plates completely 

 covered by small tubercles and miliaries ; ocular plates small, triangular, ex- 

 cluded from the anal system, tuberculated on the upper edges. Sutural pits at 

 the junction of ocular and genital plates. Anal system covered by small plates 

 irregularly arranged, one of which is 'more prominent than the others. The 

 color of the tuberculiferous part of test as in previous specimen ; the bare 

 interambulacral space is gray along the median sutures, with a dark violet 

 edge towards the poriferous zone and along the horizontal sutures. 



In younger specimens, 18.5 mm - in diameter, the differences are considerable. 

 The ambulacral system and adjoining tuberculiferous portion of the inter- 

 ambulacral system bulge out far beyond the re-entering bare median interam- 

 bulacral space ; the outline from above is regularly pentagonal, with rounded 

 angles and deeply re-entering sides. The abactinal system is very large in 

 proportion, carrying tubercles only adjoining the anal system. The genital 

 openings are placed in crescent-shaped cuts on the outer extremity of the 

 genital plates. The ocular plates are proportionally larger, and nearly touch 

 the anal system; the interior angle of the ocular plates is occupied by a 

 deep pit separating the adjacent genital plates. The tubercles of the ambu- 

 lacral region only cover the outer edges, leaving a bare median space and 

 bare horizontal sutural spaces separated by a small triangular patch of 

 tubercles ; the median sutural pits are scarcely marked in both areas, but 

 the deep horizontal sutural pits of this stage of growth give to these smaller 



