2<S 
undulate ; walls strongly corrugate. Corallites very long, up to eight inches, 
parallel. Epitlieca coarsely striate. Corallite chains highly farcimentiform, 
often contiguous laterally. Autopores very large, oval to circular, the latter 
forming a conspicuous feature ; from one to six in each corallite chain, the 
average being four, from one and a half to two millimetres by one to one and 
a half millimetres in diameter, or at times possessing the same diameter in 
both directions ; visceral chambers transversely elongate (parallclogrammatic) ; 
tabulae complete, distant, and very regular, horizontal, or slightly concave, 
half to three-quarters of a millimetre apart. Gonopores quadrangular, 
polygonal, or variable in form, sometimes absent at the chain junctions, but 
when present, always much larger than the mesopores ; walls as thick as 
those of the latter ; visceral chambers nearly square ; tabulae complete, 
equidistant, horizontal, one-third of a millimetre apart. Mesopores numerous, 
in short but very marked re-entrant spaces, transversely elongate (parallclo- 
grammatic), but not slit-like, half to three-quarters of a millimetre in 
longitudinal measurement by one-quarter to three-quarters of a millimetre 
transversely ; visceral chambers longitudinally elongate (parallelogrammatic) ; 
tabulae complete, horizontal, one-quarter millimetre apart. 
Obs. — H. cratus is a strong and robust species, possessing the largest 
autopores of any of our Halysites, and by the almost circular outline of the 
latter is readily recognisable. As in II. orthopleroides, the corallite chains 
are very farcimentiform, but whereas the individuality of the autopores arises 
from the interpolation of long mesopores in the latter, in the present instance 
the re-entrant spaces containing the mesopores are short, and the sausage-like 
outline of the corallite chains sensibly increased thereby, and the rotundity 
of the autopores rendered very conspicuous. 
The colonies form large tabular masses like those of II. peristepliesicus , 
and possibly also II. orthopteroides, but exceeding both in the length of the 
corallites, and in consequence height of the corallum. 
II. cratus is a most interesting species from the fact that many of the 
chains do not always take their origin from and junction with a gonopore at 
their opposite ends, but sometimes by the simple interposition of a mesopore. 
At the same time, gonopores are present both in numbers and normal 
position ; and not only of large size, but in some instances surrounding the 
chief zooid are other smaller accessory tubes, producing a minute and limited 
ccenenchyma. When a corallite chain junctions with a mesopore, the latter 
only differs from the ordinary mesopores regularly interpolated between the 
