Zooruyva. | LOWER PALAZOZOIC RADIATA. 13 
space of one line; upper and under surface of slightly weathered specimens shewing vertical, vermicular 
perforations about one-fourth of a line in diameter, passing nearly at right angles through the numerous 
layers composing the mass, at distances varying from one to two lines apart. 
This exclusively Silurian species has been confounded with the exclusively Devonian Stromatopora con- 
centrica of Goldfuss by Mr Lonsdale (Silurian System, &c.), and by Prof. Phillips (Paleozoic Fossils, Memoirs 
of the Geological Survey, Vol. II. &c.) but has been briefly distinguished by @Orbigny, in his recent “ Pro- 
drome,” on account of the greatly fewer number of the layers in a given space, and more delicate nature of 
the reticulation; a conclusion to which I had independently come before receiving his volume, using the 
same character as an easy mode of distinguishing the Stromatopora of Newton Bushell (Devonian) limestone 
from that of the Silurian limestone of Wenlock. It may be well to state that I derive my notion of the 
true S. concentrica of Goldfuss from authentic specimens from the Eifel. One specimen, partially weathered, 
from the Wenlock limestone of Wenlock edge, shews most clearly on its upper and under surfaces and crossing 
the vertical edges of the mass, the long tube-like perforations which have escaped general observation, and 
which in the more compact and better preserved specimens can scarcely be seen. 
Position and Locality—Abundant in the Wenlock limestone of Wenlock, Shropshire; also in the 
Aymestry limestone near Aymestry, Herefordshire. 
srd Ord. ZoantTuHaria (Blainv.) 
= Zoophyta helianthoidea (Johnston) = Actinaria (Dana). 
Animal with simple tentacles, perforated at the tip, and either six (Antipathacea), twelve (Madreporacea), 
or a larger number (Madrephyllacea). The individuals are either simple or compound, and either fleshy 
and naked, or with a strong internal, supporting calcareous corallum. The body is in all cases distinetly 
radiated by vertical, double, membranous lamelle extending from the short central stomach to the outer 
wall; which lamellae becoming calcified at the base in those possessing a corallum, form the stellate 
cells therein; each cell of the corallum is continued in the living state into a perfect individual. In the 
extreme young state, most coral-cells have six lamellze, and this number remains through life in the Ist Tribe, 
Antipathacea: subsequently a second cycle of six shorter lamellze is developed, one between each pair of larger, 
and this number remains permanent in all the genera of the 2nd Tribe, Madreporacea. In the other groups 
additional lamellz are intercalated between these. Mr Dana notices that in those groups which are more 
than twelve-rayed, there are usually three smaller between each pair of larger lamellee, and the number 
is a multiple of four, if over twenty-four; below this, if more than six, the lamellz are usually alternate, 
and the number a multiple of six. The Zoophytaria haying eight equal tentacles, and rays to the cells, 
belong to a different system. 
The Order is divided into the following Tribes: Ist, Antipathacea, having six tentacles and a horny 
axis, of which we have no fossil examples; 2nd, Madreporacea ; 8rd, Madrephyllacea. 
2nd Tribe. MADREPORACEA. 
Corallum composite ; composed entirely of cellular, or porous, calcareous sclerenchyme; cells small; each cell 
with six primary cellulose, lamellze in the young state, usually receiving six alternating or secondary lamellee when 
adult, total number never exceeding twelve; interlamellar structure composed of small, irregular, often rudi- 
mentary vesicular plates, never forming diaphragms ; cells remaining unfilled at base by age ; no epitheca. 
This Tribe contains the families, 1 Madreporide ; 2 Poritide ; 3 Palawoporide. 
To this tribe I provisionally refer the genus Pa/wopora on account of the twelve radiating lamellz to the 
cells ; a number so characteristic of the Madreporacea generally, with which it also agrees in the cellular texture 
intervening between the individual stars. The main difference between the Palwopore and the true Madrepores 
