34 Dr. T. Wright on new Species of Echinodermata 
posed in a triple oblique series of pairs ; the mouth is large and 
pentagonal ; the anal plates form a narrow prominent ring at the 
vertex, and the interambulacral areas are in general divided by a 
median depression. 
Polycyphus nodulosus, Minster. 
Syn. Echinus nodulosus, Goldfuss, Petrefact. Ger. tab. 40. fig. 16 ; 
Agassiz, Cat. Syst. p. 12. 
Arbacia nodulosa, Agass. Prodrom. 
Polycyphus nodulosus, Agass. & Desor’s Cat. raisonné, Ann. Scien. 
Nat. tome vi. p. 361. 
Test hemispherical ; ambulacral areas a little more prominent 
than the interambulacral areas ; ambulacra with from four to 
five rows, and interambulacra with from twelve to fourteen 
rows of small tubercles disposed in nearly parallel lines ; bases 
of the ambulacra with twelve, those of the interambulacra 
with sixteen larger tubercles. 
Height 7,ths of an inch, diameter 33ths of an inch. 
This pretty little Urchin was first described by Prof. Goldfuss 
from specimens named by Count Miinster from the Oolites of 
Baireuth ; the hemispherical test exhibits a disposition to assume 
a subpentagonal circumference from the greater prominence of 
the ambulacral areas; the surface of the test is divided into 
fifteen nearly equal lobes by the ten poriferous avenues, and the 
five depressions which divide the interambulacra down their 
mesial lines ; these lobular divisions are more defined in young 
and small specimens than in large and old ones; the ambulacral 
areas are one half the width of the imterambulacral, and have 
nine large tubercles at their base, and four or five rows of small 
tubercles at their widest part, which gradually diminish to three, 
two and one as we approach the apex of the area ; the interam- 
bulacral areas are twice the width of the ambulacral, they have 
about twenty-four large tubercles at their base, and about twelve 
rows of small tubercles at their widest part, which gradually 
diminish by the disappearance of the external rows to ten, eight, 
six, four and two, as we trace the rows from the equator to the 
apex of the areas; the tubercles on the sides and upper surface 
of the test are nearly of a uniform size, they are arranged in 
rows, the tubercles are opposite each other and do not alternate 
as in some other genera. The interambulacral areas are each di- 
vided by a slightly depressed line into two lobes ; these are sepa- 
rated from the ambulaeral areas by straight narrow poriferous 
avenues, so that the test of this beautiful Urchin appears to con- 
sist of fifteen nearly equal lobes, those of the ambulacra being 
the most prominent and best defined, in consequence of the 
