248 ECHINODERMATA—ECHINOZOA SUB-BRANCH III 
SECTION D. APETALA. 
Ambulacra flush, apetalous, generally uniporous, and either similar or diverse ; 
plates high, few, often heaagonal. Fascioles usually present. 
Under this head are included the following recent genera, all but the first 
two of which have fascioles : 
—Genicopatagus, Palaeobrissus, 
A. Ag.; Aceste, Wyv. Thom- 
son ; Aérope, Norman ; Palaeo- 
tropus, Lovén; Homolampas, 
Argopatagus, A. Ag.; and 
Cleistechinus, de Loriol. 
Miocene. 
Family 3. Leskiidae. Gray. 
Test thin, ovoid. Apical 
system with three basal plates 
fused into one. - Peristome 
eccentric in front, pentagonal, 
with five angular buccal plates. 
Palaeostoma, Lovén 
(Leskia, Gray). Recent; 
China, East Indian Islands. 
Family 4. Pourtalesiidae. 
Loven. 
Test very elongate,  sub- 
cylindrical or obconical, truncated 
anteriorly, flat actinally.  Peri- 
stome in a deep anterior recess ; 
periproct actinal, or above the 
projecting posterior rostrum 
when such is present. Ambu- 

Fic. 402 dis. lacra flush, apetalous, sometimes 
Macropneustes Meneghinii, Desor. Eocene; Monte Spiado, near discontinuous ; pores single or 
i a slit-like 
Pourtalesia, Spatagocystis, Echinocrepis, A. Ag. Recent. 
Range and Distribution of the Echinoidea. 
Fossil Sea-Urchins make their appearance as early as the Ordovician, but 
are represented very sparsely by forms differing in a marked degree from the 
normal (Bothriocidaris, Echinocystites). The order Perischoéchinoida, character- 
ised by its supernumerary columns of plates, is widely, but by no means 
numerously, distributed in the Devonian and Carboniferous of North America 
‘and Europe. 
Fragmentary remains of true Cidarids are found in the Permian, perhaps 
