10 
DESCRIPTION OF SPECIES 
ANTHOZOA 
Genus, Streptelasma Hall 
Streptoplasma Hall, Pal. N.Y., vol. I (1847) (Changed to Streptelasma) ; Strepielasma 
Milne-Edwards and Haime. Mon. d. Polyp. Foss. d. Terr. Pal. (Arch, du Mus. d'Hist. 
Nat., 5), p. 398 (1851); Dybowaki, Archiv. f. Natur. Liv.-Ehst. und Kurl., 5, p. 381 
(1874); Nicholson, Rept. Pal. Ont., pt. 2, p. 26 (1875); Rominger. Geol. Surv., Mich., 
vol. 11% pt. 2, p. 140 (1876); Nicholson and Etheridge, Mon. Sil. Foss. Girvan Dist., 
p. 67 (1878) ; Lambe, L. M. : Geol. Surv., Canada, Con. Can. Pal., vol, IV, pt, 2, p. 107 (1901). 
Owing to the imperfection of some of the specimens examined the 
genus Streptelasma has been distinguished by several more or less contra- 
dictory characteristics. The original description by Hall differentiates 
it by the central twisting of the primary septa. Later, Milne-Edwards 
and Haime add to the description the incompleteness of the development 
of the tabulae, but characterize the lack of epitheca as of generic value. 
Dybowski rightly assigns the lack of an epitheca to poor preservation and 
adds to the generic characteristics the pseudo-columella formed by the 
central twisting of the primary septa, frequently resulting in a boss in the 
bottom of the calyx, giving as the two differentiating generic distinctions 
the tabulae arranged in more or less regular horizontal planes occupying 
the whole visceral chamber, and the absence, near the margin of the cup, 
of the vesicular tissue which characterizes certain of the Cyathophyllides. 
Nicholson stresses as characteristics the poor development of the tabulae 
and the total lack of dissepiments; later he notices the presence of infre- 
quent dissepiments. Rominger first notes the presence of an inconspicuous 
septal fossula, a feature which in some cases makes it difficult to distinguish 
from Zaphrentis, of which he considers it a subgenus, regarding the differ- 
ences as a matter of degree rather than of kind. Lambe distinguishes 
the two genera by the completeness of the tabulae and the conspicuousness 
of the septal fossula in Zaphrentis. 
The history of the form of the descriptions, then, lies in the fact that 
early writers considered it necessary to distinguish Streptelasma from 
Cyathophyllum and stressed the lack of the vesicular zone in the margin 
to the exclusion of all dissepiments. Later writers, with a wider range 
of species, found closer affinities with Zaphrentis and stressed such affinities 
and differences. There is also some confusion in the use of terms. 
.Dybowski says the irregular tabulae fill the visceral chamber, possibly 
including some forms of Zaphrentis of which his generic characteristic was 
the presence of the fossula. Other later authors describe the genus with 
a few dissepiments and interrupted irregular tabulae. Lambe says 
“no true tabulae, their place being taken by dissepiments'’. It is a matter 
of interpretation whether the irregular, frequently inclined partitions 
dividing the interstices between the septa are true dissepiments or 
incomplete, irregular, poorly-developed tabulae. 
The constant characteristic differentiating Streptelasma from Zaphrentis 
seems to be the vesicular cellulose central region, although Streptelasma 
in common with Zaphrentis has a pseudo-columella formed by the twisted 
ends of the primary septa, and in some cases a few marginal dissepiments. 
Some species possess a septal fossula, though commonly it is less 
conspicuous than in species of Zaphrentis. 
