ACTINOPOEA. 
7 
PI. I. Pig. 2. A zoarium intermediate between the typical 
A. Irongniarti and A, cretacea, d’Orb. ; x 10 dia. Upper Chalk : 
south-east of England. Purchased from E. H. Butler. D. 4477. 
Affinities. 
This Actinoporan occurs in two forms, which appear to me to he 
only varieties, due possibly to differences in the depth at which 
they grew. Milne- Edwards founded the species under the name 
Tuhulipora Irongniarti on a specimen from Meudon, in which the 
rays are long and some of them may be uniserial ; but some of the 
rays expand into triserial groups, which are distinctly triangular, 
passing from a central uniserial to an outer multiserial condition. 
Unfortunately most authors have taken a form with long narrow 
biserial rays as A. h'ongniarti\ but Milne-Edwards’ figure leaves 
no doubt as to the characters of his species. 
A second variety was described by d’Orbigny as Actinopora 
cretacea ; it has a broad peripheral zone of small zooecia, and the 
rays are usually biserial. I was at first inclined to regard this as 
a distinct species, but a specimen (D. 4477) shown on PI. I. Eig. 2 
has some short, triangular, multiserial rays between the biserial 
rays. Such specimens indicate that A. cretacea is a variety of 
A. Irongniarti. D’Orbigny ’s A. diademoides necessarily follows 
with A. cretacea^ as it appears to be only a form in which the 
margin overhangs. 
A. hrongyiiarti is allied to A. diadema (Goldf.), as both have 
sometimes triangular, triserial rows of apertures ; but in A . Irong- 
niarti the rows are long and low, whereas in A. diadema they rise 
in short, tooth-shaped groups, resembling Discofascigera. 
LIST OE SPECIMENS. 
British. 
D. 3098. A zoarium of the typical Meudon form, attached to a fragment of 
Echinocorys scutatiis, Leske (on slide). Upper Chalk. Dover. 
J. S. Gardner Coll. Pigd. PI. I. Pig. 1. 
D. 4477. A zoarium of the variety intermediate between the typical A. brmig- 
niarti and A. cretacea, A’ attached to an echinoid plate. 
Upper Chalk. South-east of England. Purchased from P. H. Butler. 
Pigd. PI. I. Pig. 2. 
D, 4456. Two very young zoaria on an ossicle of Bourgueticrinus. Upper 
Chalk — zone of Micraster coranguinwn. Gravesend, Kent. 
Wetherell Coll. 
