10 
former, tabulae complete, horizontal or curved, but closer in the mesopores 
than in the autopores. Refers to the presence of septa and absence of meso- 
pores in II. esch avoid es. Subscribes to the dimorphic theory of Nicholson, 1 
and supports it by figuring a II. catenularia, with mesopores, and with 
spiniform septa in one of the autopores. 
1896. — Sardesson (F. W.). 2 — This author uses the term autopore for 
the largest corallites in a chain, as here adopted, but Nicholson’s interstitial 
tubuli are termed siphonopores, one between each pair of the former, in 
II. catenularia, Linn. lie describes pseudo-septa and close, horizontal, or 
oblique tabulae in the autopores, and states that budding takes place chiefly 
from the chain junctions (gonopores, mihi). In U. escharoides there are 
twelve pseudo-septa, meeting at their distal ends, but mesopores are “ seldom ” 
developed. 
1899. — Lam.be (L. M.). 3 — No writer has more forcibly recognised the 
great difficulties attending the discrimination of species in this genus than 
Mr. Lambe. He states that the structure of Canadian specimens does not 
bear out Nicholson’s method of distinguishing the species by their internal 
structure — the presence or absence of both spiniform septa and secondary 
corallites (mesopores). 4 It must not be forgotten, however, that Nicholson 
confined his remarks to the two Edwardsian type species. 
As II. catenularius proper, Mr. Lambe figures a coral with autoporal 
spiniform septa and mesopores ; the tabulae of the autopores are horizontal or 
slightly concave, and those of the mesopores close-set, strongly arched, and 
almost at times vesicular. The last condition shows a remarkably close 
affinity to Fischer-Benzon’s longitudinal section of II. cavernosa, F.-B. Var. 
quebecensis, Lambe, differs by possessing narrow mesopores with distant 
horizontal tabulae, and in the absence of the spiniform septa of the species in 
chief. Var. gracilis, Hall, is without mesopores, but autoporal septa are 
present, and the tabulae are distant, horizontal, concave, or rolling. Var. 
simplex, Lambe, possesses very large autopores, questionable spiniform septa, 
and no mesopores, the tabulae are wide apart, horizontal, concave, rolling, or 
sub-vesicular here and there. Var. amplitabulata , Lambe, is a very interesting 
form in which the mesopores are “as large as and even larger than” the 
1 Nicholson, Tab. Corals Pal. Period, 1879, p. 230. 
- Sardesson, Neues Jalirb. Min., Beil. Bd. X, 2 Heft, 1896, p. 272. 
3 Lambe, Contrib. Canadian Pal., IV, Pt. 1, 1899, pp. 64—78. 
4 Lambe, Loc. cit., pp. 66 and 67. 
