34 
Halysites peristephesicus, 1 sp. UOV. 
(Plate II ; Plate VIII, Figs. 1 and 2.) 
Sp. Char . — Corallum forming large, thick, tabular masses up to two 
feet long, consisting of long parallel corallites ascending from an extended 
base of attachment. Fenestrules linear, labyrinthine, or convolute, often very 
long and clustered, or almost revolving around certain given centres; sizes 
2x2 mm., 6x2 mm., 13 x 1 mm., 18 x 1 mm., 23 x 1 mm., &c. ; margins 
very undulate ; walls strongly corrugate or ribbed. Epitbeca fine, transversely 
striate. Corallites long, straight, up to six and eight inches. Corallite chains 
varying from short to very long, the latter predominating, strongly farci- 
mentiform. Autopores large, from two to twenty in a chain, hut with no 
definite average number, broad oval in outline, with bulging sides, one 
millimetre, or slightly more in longest diameter, by three-quarters of a 
millimetre ; septa short, in one or two cycles, not developed on the mesoporal 
walls; visceral chambers generally transversely elongate (parallelogrammatic) ; 
tabulro complete, very regular, horizontal, or occasionally oblique, half a 
millimetre apart. Gonopores large, very irregularly polygonal, as a rule much 
longer in one direction than the other, non-septate ; visceral chambers nearly 
square ; tabula) complete, horizontal, one-fifth of a millimetre apart. Meso- 
pores well developed, transversely oblong, non-septate ; tabulae complete, 
horizontal, one-fourth of a millimetre apart. 
Ohs. — This is a large and very beautiful form of Halysites, and is 
remarkable for the length and linear appearance of its fenestrules, and so 
presenting a very marked contrast with II. pycnoblastoides. Mr. C. A. 
Sussmilch informs me that he saw a colony in situ which measured two feet 
long by five inches high and ten inches wide, and showed the extended flat- 
based tabular form to perfection. No other Australian Halysites that I have 
seen is of so compact a growth with similar long parallel corallites. 
Another special feature in this species is the strange tendency the 
corallite chains seem to have of encircling, hardly revolving, round certain 
centres 2 ; in fact, when viewed as a whole the corallum appears to be made up 
1 Ilfpio-Ted));? — “encircling an object.” 
2 Since this description was written, I have seen Mr. R. P. Whitfield’s interesting paper — “Observations 
on a remarkable specimen of Halysites,” &c. (Bull. American. Mu. s. Nat Hist., 1903, XIX, p. 489), in which 
he describes a form referred to H. catenulatus, Linn., presenting on its upper side the original surface of the 
coral in about the condition it had while living in the “Silurian seas,” and possessing on its upper surface 
seven “ botryoidal or convex bosses ” (loc. cit. pi. xli, pi. xlii, f. 5.) Mr. Whitfield further remarks on the 
elongation and compression of the “ cell spaces ” (our fenestrules) in the spaces between the “ bosses.” This is 
also noticeable in the corresponding spaces on the Australian specimens between what I have termed “rosettes” 
(PI. ii, Fig. 3). On the other hand, the upward tooth like extension of the cell walls seen in the American 
examples is not present, possibly on account of the state of preservation. 
