10 
CRETACEOUS ECniNQDERlMATA 
I. Ctf««5.—nEMI ASTER, Desor, 1817. 
The Spatangoids, included in this genus, ai’c mostly of small size, angularly or 
roundly ovate, and of moderate height; tlie petals or aml)ulacra are depressed, 
generally unequal, the anterior always traceable, though not equally developed as the 
other four; they are surrounded by a peripctal fasciole; the mouth is transversely 
kidney-shaped, with slightly thickened entire lips; the anus posterior near the upper 
end, and vertically roundly ovate ; the genital apparatus is solid and composed of 
four plates with comparatively large round openings; surface more or less distinctly 
tubcrculated and granular ; the tubercles on the upper or iutcr-amhulacral areas are 
often slightly larger, or at least more distant, than those near the periphery. 
llemiaater is one of the most widely distributed genera, being represented 
by numerous species both in cretaceous and tertiary deposits, though more common 
in the former. Eleven species of the genus occur in the South Indian cretaceous 
rocks; one was described by D’Orbigny, and three as by Eorhes. Those 
of the latter author were first referred by D’Orhigny to Uemiasler, and then by 
Desor to Feriastcr, \mi D’Orhigny’s generic determination appears to he the 
correct one — at least, as far as I have been able to satisfy myself by the examination 
of authenticated specimens. 
1. IIemiaster similakis, SloUczka. PI. I, Fig. 1. 
U. testa depresse ovnta, postice angustatim suhtruncata, supra 'panto convexins- 
cula, nndique moderate tuberculata ; apice centrali ; amhulacris lateralihus pro- 
funde impressls, suhlcecigatis, truncatis, hiccqualihus, antero-lateralibus miilto 
majoribus, antico longisswio sed eoiteris minus profundo, granulose tuberciilato, de- 
pressione prope peripheriam fere obsoleta. 
Test depressed, slightly convex above, almost regularly ovate, with rounded 
perqfiiery, suhtruncate posteriorly, and the anal end somewliat higher than the 
oral. The anterior ambulacrum is the longest of all, moderately deep, of equal 
width throughout, shallowing out almost entirely towards the margin ; the plates 
in it are covered with small tubercles and numerous granules ; there arc 28 pairs of 
pores in each row, the last more distant than the others, and the ])ores in each pair 
are separated by a very distinct small gi-auulc ; the remaining ambulacra! plates 
beyond the fasciole are much elongated, and each has in the outer anterior angle a 
pair of very small pores. The lateral ambulacra are very deep, broad, truncate, 
very finely granulated ; each postero-lateral is only three-fifths of the length of an 
antero-lateral; the latter diverge rmder an angle of 98 degrees, and have in each series 
about 40 pairs of pores, while the former diverge imder an angle of (52 degrees, 
and each series consists of only 25 pairs of pores. The fasciole is of a similar shape 
as the test, slightly contracted at the posterior sides. 
( 80 ) 
