ON THE BRITISH FOSSIL CORALS. 107 
shaped, and have a great range. It would appear that the following Table 
gives a correct idea of the dispersion of the early 7'hezosmilie. 
—= Azzarola, species ... |= Species of the Luxembourg and 
St.-Cassian types... | A. planorbis, species French Zone of A. angulatus. 
A. angulatus, species ——* Oolitic species. 
The genus Llysastrea has its corallites separate and covered with an 
epitheca below, but united above at the calicular margin. The calicular part 
is clearly Isastraean, and the basal is Thecosmilian. Now bush-shaped 7’he- 
cosmilie, such as T, Michelini and T. Martini, are noticed to become united by 
their walls in some individuals, and the walls of some species of genera 
closely allied to Zsastrwa are not united inferiorly. 
The genus is clearly a transition, not only between T'hecosmilia and 
Isastrea, but between several groups of genera. For instance, 
Thecosmilia—Elysastr ea—Isastrcea—Latimceandrea. 
Montlivaltia —NSeptastreea, 
—Prionastreea. 
The earliest reliable Isastree are from St. Cassian ; and several species are 
found with the St.-Cassian Elysastriean ; but they are all erratic and rather 
abnormal forms. Thus Jsustrea Haueri, Laube, and J. splendida, Laube, have 
a very irregular calicular development, and not one of the Liassic species 
ever attained that regularity of septal arrangement which characterizes the 
Oolitic Isastreeans. 
In the Sutton stone, at Brocastle, in Skye, and in the Worcestershire beds 
of Ammonites angulatus, there are the following Isastree. 
Tsastrzea Sinemuriensis, De From. Isastraea Murchisoni, Wright, sp. 
globosa, Duncan. — Tomesii, Dunean. 
has deep calices, great irregularity of septal arrangement, 
78 septa, sometimes no distinct cyclical arrangement. 
spherical, calices shallow, sometimes 36 septa, but no cy- 
1 clical arrangement. 
large, convex, flat, calices shallow ; wall grows after the 
I. Sinemuriensis { 
I. globosa, 
I. Murchisoni, development of the contiguous calices; 40 or more 
septa ; no cyclical arrangement. 
ence, large, massive ; wall thin; septa thin, with dissepiments 
between them visible; not 4 cycles. 
The first of these species has a great range, and connects the St.-Cassian 
and Oolitic species with a high septal number. 
The second belongs to a series comprising 
I. Richardsoni, Ed. & H., Inf. Oolite. 
I. dissimilis, Mich., sp. 55 
The third has evident affinities, from the structure of the wall, with Ely- 
sastrea and Lepidophyllia, and it is an unusual form. 
The fourth resembles more or less J. Bernardiana, Ch. and Dew. Inf. 
Oolite. 
It will be observed that these species have only a remote, but of course 
generic, affinity with the Isastree of the succeeding arenaceous deposits of 
the zone of Ammonites Bucklandi, but that their affinities with the species 
of the St.-Cassian and Inferior-Oolite coral-faunz are decided. 
They have only a generic relation to Isastriea latimeandroidea, Duncan, of 
the zone of Ammonites planorbis, as no serial calices are found in them. 
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