87 
It differs from P. humboldtensis Gabb 1 of the Middle Triassic of 
Nevada in its somewhat larger size, more angular posterior extremity, and 
much less definite concentric growth ridges. In outline of valve and in 
posterior extremity it resembles Anoplophora munsteri Wissem 2 of the 
lower Karnic (Cassian), but has fewer growth ridges than are present in 
our species. 
Megalodon canadensis n. sp. 
Plate IX, figure 3 
Shell subcircular in outline. Length from beak posteriorly 90+ mm., 
breadth from hinge-line to base 70 ± mm., thickness of entire shell 50 ± 
mm. Beaks anterior, strongly incurved. Surface marked with numerous 
concentric growth lines, some six of which, inequally spaced, are con- 
siderably stronger than the others. Cardinal teeth probably large, situated 
upon a strong, broad platform extending posteriorly from the beak. The 
cavity formed beneath this dental platform is continued posteriorly by a 
very pronounced inbending of the shell at the hinge-line; whether this is 
due to a postero-lateral tooth our specimens do not say. This groove gives 
to internal moulds a very characteristic appearance. 
Similar to Megalodus subdrcularis Koken 3 from the middle Keuper 
(Gipskeuper) of the southern Tyrols in general shape, but our specimen is 
larger and the groove formed between the lateral tooth ? and the shell is 
much narrower, giving an internal mould of very different shape. 
Myophoria sp. 
Shell large, diameter 2 to 4 inches, with discrepant ornamentation. 
Turdcula mccanni n. sp. 
Plate IX, figure 5 
Small, length of five coils (tip of shell is wanting) 22 mm.; breadth of 
largest coil 12± mm., of next coil 10 mm. Whorls angular, their slope less 
above (posteriorly) than below, the angles beset with somewhat oblique, 
conspicuous knobs, about 12 encircling the 10 mm. whorl. There is a slight 
ridge at the junction of the whorls. Faint spiral growth lines are present, 
and probably also oblique ones. Since both these oblique growth lines and 
oblique knobs are directed downward to the left, the shell may be sinistral. 
Named after Dr. W. S. McCann, who discovered this Pearson Creek 
fauna. 
Our single shell belonging to the Trocho-Turbinidae family resembles 
Turdcula tuberculata Koken from the Karnic (obere schichten des Rothel- 
steins). 4 The proportion of length to breadth of the whorls is about the 
same. It also has about 12 knobs encircling one whorl. But the shell is a 
1 Smith, J. P-, “The Middle Triassic Marine Faunas of North America," U.S. Geol. Surv., Prof. Paper 83, 
p. 143, PI. 16, fig. 14. 
* Bittner, A., "Lamellibranchiaten der alpinen Trias," Abhand. der K. K. Geolog. Reiohaanstalt. Wien, Bd. 
18, p. 9, Taf. 1, figs. 22-26. 
1 Koken, E., “Beitrage zur Kenntnis der schiohten von Heiligenkreui," Abhand. der K. K. Geolog. Reicbsan- 
stalt. Wien, Bd. 16, Taf. 5, figs. 2, 2a, b. 
4 Koken, E., “Die Gastropodon der Trias um Hallstatt,” Abhand. K. K. Geolog. Reiohaanstalt. Wien, Bd. 17, 
Heft 4, p. 57, Taf. 19, fig. 13. 
