PERMIAN FOSSILS. 
Or 
w 
Cyathocrinus ramosus occurs rarely in the Shell-limestone at Tunstall Hill and 
Silksworth; abundantly in the corresponding rock at Humbleton Hill; and rather 
uncommonly in the Breccia at Tynemouth. Geinitz records its occurrence in the 
Lower Zechstein of Corbusen; and in the Zechstem-Dolomite of Asbach, Schmal- 
kalden, Posneck, and Kamsdorf. According to Schlotheim, it is found at Glicksbrunn 
and Liebenstein. 
Order KCHINIDE, Cuvier. 
This order, of which the common Sea-urchin (fehinus esculentus) of the English 
coasts is a good representative, consists of a large number of genera, both living and 
extinct; but the following one is the only form known to be Permian. 
Genus Archeocidaris, M‘Coy. 
Diagnosis. —“ Interambulacra composed of three or more rows of plates, those on 
each side, next the ambulacra, pentagonal; those of the immediate rows hexagonal, as 
in Palechinus ; each plate having in the centre one large perforated tubercle, surrounded 
by an elevated ring, as in Cidaris, each of which tubercles bears a large, mobile, 
generally muricated spine.”’ (M‘Coy.) 
“Tt is a singular circumstance that, except Professor Agassiz, every author who 
has treated of the Achinodermata of the Mountain-limestone, should have referred the 
hexagonal plates with the above characters to the genus Cdaris, when a glance at the 
recent or Oolitic Cidarites would be sufficient to show that in their entire framework 
there is not one hexagonal plate, both the ambulacra and interambulacra being composed 
each of fwo rows of pentagonal plates only, while'in the present genus, as in Palechinus, 
their interambulacra must have been composed of more than two rows, as is obvious 
from their hexagonal form; the large, perforated tubercle, however, is precisely in 
accordance with that of the true Crdaris, as is also the mode of attachment and 
general character of the large spies with which both genera are armed....... I 
had long ago distinguished this genus in my MSS. under the name of Archeocidaris, 
subsequently Professor Agassiz announced his intention of forming the genus Hehinocrinus 
for the Cidaris Nerit, &c.”? 
Though Agassiz’s name is adopted by Professor M‘Coy, yet later writers, from the 
circumstances above related, have been led to give the preference to the name 
Archeocidaris. M. Agassiz, with his colleague M. Desor, has lately changed the name 
into Paleocidaris. 
! Carboniferous Limestone Fossils of Ireland, p. 173. 
2 Idem. 
