7 
of distinguishing individual species from one another, or at least of dividing 
them into definite groups. The size or even the shape of the individual 
calices is much less important.” And again, “ The nature and construction of 
the dividing walls can supply a means of separating the species of Halysites 
into several groups.” According either to his descriptions or figures, the 
corallites (autopores) are separated (a) by two pairs of vertical bars, or “rods,” 
arising from the main chain walls and meeting in the centre, each pair, with 
the assistance of the latter, thus enclose between them one of Nicholson’s 
“ interstitial tubuli,” or, as I here term them, mesopores ; 1 ( b ) at times these 
“rods” blend into a single partition at each end of an autopore ; 2 ( c ) the 
longest diameter of these rods may be either parallel to or at right angles to 
the direction of a chain of corallites ; 3 (d) after blending, the walls may he so 
thickened as to all but obliterate the visceral chambers of the mesopores ; 4 
(c) the blending may proceed to such an extent as to ultimately obliterate 
the intermediate chamber, or mesopore . 5 
The principal points brought out in the specific descriptions are the 
following: — Halysites cavernosa, F.-B., possesses both complete and 
incomplete tabulae in the autopores, and there are no spiniform septa ; the 
mesopores arc highly vesicular. In II. regularis, F.-B., the tabulae of the 
autopores and mesopores are practically complete and normal ; hut the 
structure of the “rod” walls of the latter is peculiar, and if constant, 
characteristic of the species. In his conception of II. labyrinthica , Goldf., 
the tabulae of the autopores are at times very incomplete and highly 
vesicular, the vesicles large, but those of the mesopores are normal. 
H. obliqua is a septate form, with the peculiarity that certain of the septa 
proceed from the transverse dividing walls between the autopores ; there is 
no clear evidence of the presence of mesopores. H. approximate, Eichw., is 
said to possess numerous complete (“single”) tabulae. In H. par allela, 
F. Schmidt, the tabulae are concave (“bent down”). Fischer-Benzon’s 
conception of H. eschar oides, Lamk., presents several points of very great 
interest. In the first place, the septa are said to blend at their inner or 
distal ends into a false columella, often so strongly developed as to become 
exsert ; there are five cycles in a visceral chamber. The mesopores are either 
1 Fischer-Benzon, Op. cit., pi. i, f. 2 and 9. 
2 Ibid., op. cit., pi. ii, f. 5 ; pi. iii, f. 2. 
* Ibid., op. cit., pi. i, f. 9 ; pi. ii, f. 2 and 
4 Ibid., op. cit., pi. iii, f. 3. 
5 Ibid., op. cit., pi. iii, f. 2. 
