154 CLASS IV. 
Nucleolites Lam. Body ovate or cordate, convex, sub-irregular. 
Ambulacra five, extending radially from the vertex to the base, not 
interrupted. Anus superior, near the margin. 
All the species are fossil, partly from the secondary, partly from the 
tertiary formation. 
Cassidulus Lam. Body irregular, elliptic, ovate, or subcordate. 
Ambulacra five, circumscript, resembling a pentapetalous flower. 
Anus superior, near the margin. 
This genus also consists of fossil species from different formations ; ex. 
gr. from the chalk formation is Cassidulus lapis cancri Lam., FAuJAS DE 
St Fonp, Besch. van den St. Pietersberg, Pl. 30, fig. 1; Bronn Lethea 
géogn. Tab, XxXIx. fig. 20. 
Fibularia Lam. Echinocyamus LEsKE. Body sub-globose, with 
outline oval or orbicular. Ambulacra five short, cireumscript. Anus 
inferior near the mouth, or median between the mouth and the 
posterior margin. 
Sp. Fibularia ovulum Lam., Guerin Iconogr. Zooph. Pl. 111. fig. 5, Hchinocy- 
amus pusillus MuEuL., ForBes Brit. Starf. pp. 175, &e. From the Atlantic 
Ocean, of the size of a pea. Amongst the foreign species, according to 
Van PHELSUM, mostly American, we note Fibularia craniolaris, V. 
PHELSUM Gewelvslekken Tab. 1. f. 16—35. Also in the chalk-formation 
and in tertiary deposits species of this genus occur, 
Echinoneus LESKE, Lam. Body sub-ovate or orbicular, sub- 
depressed. Ambulacra inscribed radially in ten furrows from the 
summit to the base, not interrupted. Anus inferior, oblong, near 
the mouth. Genital pores four. 
Sp. Zchinoneus semilunaris Lam., GuER. Iconogr. Zooph. Pl. ut. fig. 2, Cuv. 
R. Anim. éd, ill., Zoophytes, Pl. xiv. fig. 1, from the West Indian Sea, &e. 
Of this genus no fossil species are known. 
Clypeaster LAM. Body oval or sub-angular. Ambulacra cir- 
cwmscript radiating from the summit, resembling a pentapetalous 
flower. Anus inferior, near the margin, or in it. Genital pores 
mostly five. 
Sp. Clypeaster rosaceus, Echinus rosaceus, L. KuE1n Dispos. Echinod. Tab. 
xvu. fig. A, Tab. xviil. fig. B, BLAINVILLE Actinol. Pl. xvi1.; from the 
Indian and Japan Seas. The shell is thick, and parted internally by 
pillars; comp. the figures in KuEin 1. 1. Tab. Xxvitl. xxrx. Fossil 
species also from the tertiary formations are known. 
