94 
Plagiostoma hazeltonense n. sp. 
Plate XXI, figure 1; Plate XXII, figures 1-5 
A very large, semiovate, somewhat oblique, moderately convex species. 
Broadly inflected on the long, antero-dorsal submargin . Hinge-margin short. 
Anterior ear longer than wide; posterior ear as long, but wider and flatter. 
The ears and most of the inflected antero-dorsal area have concentric 
growth-lines and ridges only. The remainder of the shell surface has 
radial ornament as well as concentric growth-lines: on the posterior part are 
small, narrow, wavy striations, which toward the middle of the shell become 
broad, irregular bands separated by narrow, wavy grooves; on the anterior 
part of the shell, the ornament is striate, also, rather than banded, for narrow, 
wavy, small striations are preserved on the border of the antero-dorsal 
inflected area. The ornament is weakest on the middle part of the shell. 
Height 155 mm.; length 160 mm. (eat.); thickness one valve 35 mm. 
Plagiostoma giganteum Sowerby 1 is very similar, but is more elongate 
in outline and has feebler ornament. 
One of the Silver Lake specimens is more elongate than the typical 
specimens of the species described above, and has a narrow, inflected area. 
This may be a variety of the species. 
Horizon and Locality. From talus of the middle sedimentary division 
of the Hazelton group, exposed in a cliff about 1 mile southeast of Silver 
lake, Hudson Bay mountain, B.C. 
Types : Victoria Memorial Museum; holotype, Cat. No. 7705; para- 
types, Cat. Nos. 7705 a to d. 
Trigonia guhsani n. sp. 
(Guhsan, an Indian chief) 
Plate XX, figures 2, 3 
A large, moderately convex, ovate species, much longer than high. 
The dorsal margin is about half the length of the shell. The posterior 
margin is oblique and angular. The beaks are near the anterior end. 
Anterior part of shell covered with about twenty-one narrow costse which 
turn abruptly in a postero-ventral direction adjacent to the marginal 
carina. The area has about ten radiating small costellae, which are crossed 
by what appear to have been fairly conspicuous growth-lines. This species 
belongs to the costatce section of the genus. 
Height 66 mm.; length 100 mm.; thickness single valve 14 mm. 
Trigonia americana Meek 2 from Jurassic strata near the lower canyon 
of Yellowstone river, Montana, is smaller, is not so elongate, and has 
coarser sculpture on the area. Trigonia bachelieri d’Orbigny 3 is smaller, 
has finer and more closely arranged costellse on the area and a more pro- 
nounced median carina. 
Horizon and Locality. From talus of the middle sedimentary division 
of the Hazelton group, exposed in cliff about 1 mile southeast of Silver 
lake, Hudson Bay mountain, B.C. 
Type: Victoria Memorial Museum; holotype, Cat. No. 7706. 
iSowerby, J.; "Mjnoral Conchology”; vol. I, p. 176, PI. 77. 
Goldfuss, J.; Petrefacta Germaniae, pt. 2, p. 80, PI. 101, figs. 1 a, b. 
* 12th Add. Rapt., U.S.G. and G. S. Terr., pt.I, p. 148, PI. 88, figs. 1 a, b (1883). 
* Proderone, vol. I, p. 338. 
Annales Pal., vol. 14, Fasc. 4, p. 150 (18), PI. 18 (30), figs. 6-8. 
