| Comment: | The second choice (in the third collection) is between Uraloceras Ruzhentsev, 1936 and Daubichites Popov, 1963. Shells of both these genera are ornamented by numerous revolving lirae. These are lacking in the Alaska fragment but this, I imagine is due at least in part to the loss of the shell. The internal mold shows a suture in which each prong of the ventral lobe is fairly symmetrical and nearly as wide as the first lateral lobe (characteristic of both Uraloceras and Daubichites). Paragastrioceras has more narrower prongs and Pseuogastrioceras has more asymmetrical prongs and lacks longitudinal lirae on the flanks. The main difference between the two likely genera is the presence of a ventral salient in the growth lines and constrictions of Uraloceras and of a hyponomic sinus in Daubichites. No indication of these features are present in the Alaskan specimen, hence the uncertainity. Artinskia ranges from late Orennurgian (latest Upper Carboniferous) in the U.S.S. R. through the Early Permian Artinskian Stages Synartinskia is found in rocks of the Sakmarian and Artinskia Stages. Uraloceras ranges from the early Sakmarian Stage through the Baigendzhinia Substage of the Artkinskian (Nassichuk, Furnish, and Glenister, 1965, Geol. Survey Canada Bull. 131, p. 20). It occurs in the Canadian Arctic and in Alaska (Nassichuk, Furnish, and Glenister, 1965 op. cit., p. 20; Nassichuk, 1971, Jour. Paleontology, v. 45, no. 6, p. 1015), but is most common in the Ural Mountains. Daubichites is restricted to the Early Permian (Sakmarian and Artinskian Stages); most of the Phosphoria pseudogastriocerids are referabble to this genus (Nassichuk, 1970, op. cit., p. 81-84). Based on these facts, I would suggest that an Early Permian (Sakmarian or Artinskian age for the higher beds of the type Mankomen Formation is very likely, but the lower occurrence of Artinskia?, unsupported by other evidence may be either Early Permian or very late Carboniferous. |