Collection 60ACr130, composed of several very small horn corals, probably represents the Siksikpuk formation. Both genera identified by Helen Duncan are reported elsewhere from the Siksikpuk and Tachylasma is not known from pre-Permian rocks.

Of the remaining 5 collections, one contains essentially coralline and bryozoan material (60ACr78) like that found low in the Alapah and its equivalents. This would suggest a correlation with the lower part of unit Ml₃.

The other collections contain elements of what appears to be a single fossil assemblage, composed predominantly of brachiopods, with abundant Leiorhynchus. This is a facies fauna that occurs in the "Culm" lithology nearly everywhere it is present. In relation to the measured section, these fossils could represent either the lower part of Ml₃ or Ml₁. It is quite possible that a shaly facies represents the entire Ml₁ - lower Ml₃ interval in other parts of the Lisburne peninsula.

On the other hand, because there are apparently Devonian and Permian rocks in the same general area, structural complications may have made the identification and distinction among shaly units very difficult.

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Helen Duncan reports: "These are plerophyllid corals, poorly preserved, possibly:

Sochkineophyllum sp.
Tachylasma sp.

If the generic assignments are correct, the rock are verly likely Permian."

This collection probably represents the Early(?) Permian Siksikpuk formation.

As requested in your letter of March 22, 1963, the corals that comprise this collection have been restudied. I have spent a good deal of time investigating the foreign literature dealing with the plerophyllid corals and comparing the two species that occur in this lot with forms that have been described.

I am now convinced that the more abundant coral, in which the skeletal structures seem to be almost entirely replaced by hematite or limonite, is a genuine Tachylasma. This genus is recorded only from Permian rocks.

Material for the other species, which originally was identified as Sochkineophyllum?, consists of five chertified fragments from distal parts of coralla. The matrix is chert. These specimens provide no information on ontogenetic development, and four of them are so incomplete that one cannot determine the position of the primary septa. However, these specimens obviously belong to the same species as the fifth fragment, which did yield a section that showed the septal pattern. In all the fragments, the septa are somewhat broken and offset, presumably as a result of chertification; the septum that I originally thought was a long counter actually is a long counter-lateral flanking the shorter, offset counter septum. Ufimia seems to be the only described genus that has a similar septal pattern. As Schindewolf interprets the genus, Ufimia occurs in the uppermost Upper Devonian, Visean, lower Namurian, and Permian. It is difficult to account for the Pennsylvanian gap in distribution, and I suspect the genus as presently interpreted includes homeomorphs.

The plerophyllids are an element in the "Cyathaxonia faunas," a term used by Hill to distinguish coral assemblages consisting of small nondisseptimented horn corals such as the zaphrentoids, lophophylliidids, carcinophyllids, etc., as well as Cyathaxonia. Coral faunules that belong to this category are usually found in rocks with a high percentage of argilaceous or sandy matter. Plerophyllids are a very rare component in Cyathaxonia faunas of Mississippian age. I have not seen more that 15 to 20 examples from Mississippian rocks during the course of 17 years' work on corals from all parts of the United States. W.J. Sando reports that he has run across only about a dozen specimens in his work on our western Mississippian faunas. During Mississippian time, the Cyathaxonia fauna was composed mainly of zaphrentoids such as Zaphrentites, Homalophyllites, and Hapsiphyllum, and small columellate forms including Cyathaxonia, Rylstonia, and Rotiphyllum. If plerophyllids occurs at all in Mississippian assemblages, the chances are that only 1 or 2 specimens will be present in a sizable collection containing a variety of other genera. On the other hand, plerophyllids are particularly characteristic of Permian Cyathaxonia faunas and are the only type of coral found in some collections from our western Permian. We know that several genera of pleurophyllids occur in the Permian rocks of northern Alaska, but I have not seen any specimens in Mississippian faunas of the same region.

My original opinion that the collection under consideration was probably of Permian age was based on the factors of occurrence and distribution outlined in the preceding discussion. The collections consists only of plerophyllids. There are more than 30 specimens of Tachylasma that pretty obviously came from argillaceous rock and 5 specimens of Ufimia? in chert. The absence of any genera normally found in Mississippian Cyathaxonia faunas as well as the exclusively plerophyllid composition of the assemblage are very strong, if not conclusive, arguments against a Mississippian age for the faunule. The evidence available points to a Permian assignment, but I would be the first to admit that a firm age determination must depend on getting a more diversified fauna containing diagnostic fossils belonging to other phyla. Until this can be done, it is suggested that the beds be considered of Permian(?) age.

The possibility of an Early Mississippian age for the coral collection is hardly worth considering. The associated beds carrying the Leiorhynchus fauna are, according to Tom Dutro with whom your problem has been discussed, most likely lower Upper Mississippian (Meramec equivalents). We realize that the recognition of a presumably Permian fauna in a bed that appears to lies stratigraphically between Upper Mississippian beds indicates structural complications. However, the faunal evidence strongly suggests that we are not dealing with a continuous rock succession, and it would not serve the purposes of geology to discount the probability.