28 
CRETACEOUS ECIIINODERMATA 
1. Stigmatopygtjs elatus, (Forbes). PI. V, Pigs. 1 — 8. 
1840. Kucleolites (Cassklulus) elatus, Forb., Trans. Geol. Soc., Loud., vii, p, 1C2, pi. xix, fig. 1. 
1855. Stigmatopygus elatus, U’Orb., Pal. Franj. ten', cret., vi, p. 333, pi. 929. 
1858. „ „ „ Desor, Syn. Ecbinid. loss., p. 927. 
St. testa ambitu variabili, elongate seu late ovata, atque plus minusve elata, 
apice aperturaque subcenlralibus, oppositis, ano elongato, parvo, ad terminationem 
angustatam superam depressionis pyrtformis sito, marginibus lateralihus depressionis 
analis transoerse irregulariter sulcatis ; superficie siipera atque regione longitudinali 
mediana infera minute granulifera, parte reliqua faciei inferioris crasse tubercuUfera, 
tuberculis areola distincta circumdatis ; apertura irregulariter pentagona, lubercnUs 
quinque majoribus, atque alteris paulo minoribus interposilis, ambobus elongalis, 
circumdata ; ambulacris petaliformibus, antico longissimo, duobus ptosticis brecissimis. 
Long, speeimiuis maximi 78 mm., latitudo 60 mm., altitude 33 mm. 
This species is very variable in shape and also in height, the former changing 
from elongately to rather broadly ovate, while the sides are in younger sitecinieus gra- 
dually, in older, or perfectly adult ones, rather abruptly, sloping ; the lower surface 
is flat, slightly depressed round the aperture, which is central, suhjientagonal, 
surrounded by live large, suhpiramidal, and five intermediate, smaller, elon- 
gately diamond-shaped tubercles, or leather flattened ridges. The oral ambulacra are 
well developed, each composed of three or four iiTegularly placed small pores, one 
series extending along the outer margins of the smaller tubercles, Avhich the 
ambulacra surmount ; the two branches are connected hy a few larger scattered pores. 
The Avhole uj)pcr and the longitudinal median region of the lower side are 
finely granular, the rest of the lower surface coarsely tubercular, the large mam- 
millated tubercles more or less extending on tlie oral prominences, wlnle towards 
the margins they gradually decrease in size and pass at the edges into granules. 
The apex is central or A'ery nearly so, composed of four genital plates, of which 
the two posterior and the left anterior are largely perforated, Avhile the right 
anterior or the madreporiform is largest, porose, occupying the whole centre of the 
apex, but it has not a larger opening. Ihe pctala are very xurequal, none of them 
extending CA'en within close proximity of tlie periphery. The anterior amhulacrum 
is the longest, the antero-laterals arc slightly shorter, and one of the postcro-laterals 
scarcely exceeds three-fifths of the length of the anterior impair one ; the antero- 
laterals diverge under an angle of about 145°, and the posteriors only under an 
angle of 45°. All the petals arc very much narroAved toAvards their ends, and 
the aml)ulacral space betAveen the poriferous zones is generally slightly higher 
than the adjoining interambulacral. The anus is situated at the upper, A'cry much 
narroAved, bottle-shaped depression, shalloAA'ing below as its breadth increases ; the 
lateral edges are marked Avith transverse irregular grooves ; the margin of the 
periphery beloAV the anal slit is somcAvhat liuguiformly produced. The spines are 
mostly of small size, and closely longitudinally sulcated. 
( 08 ) 
