24 
of this genus in the Linnean Society’s collection, but although it would 
be easily identified from Linnaeus’ figure (VI, Plate 4, 1749), he finds that 
it has been lost. 
Billings (1866, 33) in a footnote to his second description of Calapoecia 
anticostiensis, writes, “ This species appears to be congeneric with Syrin- 
gophyllum organum — Sarcinula organu7n. Should this view turn out to be 
correct, then the generic name must, of course, be changed.” Etheridge 
(1878) published the description of a form which he called Sarcinula 
organum Lam.; this has been shown above to be C. canadensis var. anti- 
costiensis forma arctica Troedsson. Lindstrom (1880, 36) was of the 
opinion that Calapoecia “ comes nearest to the genus Spring ophy Hum to 
which it is obviously related.” Nicholson (1889, 317-8) follows Billings’ 
opinion of C. anticostiensis, which he said “ proves to be really quite differ- 
ent from the others, and to be nearly related to the genera Spring ophy Hum 
and Thecostegites” \ and in a letter to AVhiteaves (1879, 159-9): “Cala- 
poecia anticostiensis, Billings, is not generically separate from Syringo- 
phyllum, and must stand as Spring ophy Hum anticostiense, Billings sp.” 
This conclusion, however, was not followed by later authors. Troedsson 
(1928, 120-3) and Kiaer (1930, 65) have briefly pointed out the close 
affinity of these two genera. 
The present writer has been able to examine thin sections of only nine 
specimens from various localities, referred to this species. 8 . organum is 
found from the Bala (M’Coy 1851, Marr 1885) up at least to the Leptaena- 
limestone (Lindstrom 1888). It appears rather before the general distribu- 
tion of Calapoecia^ therefore {See section on Stratigraphical and Geo- 
graphical Range). From a study of the available specimens the following 
details have been established. 
In S. organum the corallites are circular and their walls are fairly thick 
and compact; they are apparently the product of lateral amalgamation 
of septa. The septa are in some cases seen to project a little from the 
wall and probably, therefore, are produced periodically into short, blunt 
spines arising from a low, ridge-like septum in a way similar to that in 
Calapoecia. These septa are twenty-four in number. The wall is pierced 
periodically by a horizontal row of rather elongate pores. The tabulae are 
more remote than in Calapoecia and are almost always complete. They 
may run straight across the corallite, being as a rule slightly concave, or 
they may lie very obliquely. In some cases infundibuliform tabula have 
been observed. So far as can be seen the end of the funnel, thus developed, 
is closed. 
With regard to the extra-corallite structure, an interesting variation 
is found to occur in these specimens. The most primitive “ coenenchyme ” 
seen was made up of many tabula-like, horizontal diaphragms with occa- 
sional upturned processes joining them. This is indistinguishable from 
that seen in C. canadensis var. anticostiensis forma arctica. In the speci- 
mens showing this (B.M. R305il3, “ group 5a Hero, Norway,” and R30514, 
“ group 4 Oskarskal, Hero, Norway,” Plate IV, figures 5, 6) “ costae,” 
alternating with pores, extend into the coenenchyme, again, just as in 
forma arctica. Indeed, the whole appearance is so similar to that form 
that identification with it is only prevented by the number of septa, their 
