49 
Aucella gigas sp. nov. 
Plate XI, figures 4, 5, 6 
Valves resemble each other strongly in shape. Both are broad, 
flattish, and rounded ventrally. Umbones, short, obtuse, very slightly 
incurved. Ornament of obtuse, concentric costse that have a very char- 
acteristic curve. Ornament degenerates beyond 35 mm. from the umbo. 
Dimensions. Holotype, left valve — long axis, 100 mm.; short axis, 
78; semidiameter, 20; apical angle, 80 degrees; right valve — long axis, 83 
mm,; short axis, 72; semidiameter, 16; apical angle, 90 degrees. 
Locality. Zone of Homolsomites poecilochotomus, southeast shore of 
the peninsula 200 yards from the south end. 
Name. From the fact that it is the largest Aucella known. 
Aucella teutoburgensis Weerth 
Avicula (?) teutoburgensis Weerth 1884: Palaeont. abhandl. Bd. II. 
Both valves notably convex, left valve somewhat more so than right. 
Umbones incurved. The outline is characteristic. Ornament, striate. 
Locality. Zone of Yaadia lewisagassizi, on south shore of a little point 
on the west side of Cascade bay 1,090 yards south of the north end of that 
bay. 
Family, trigoniidae 
Genus, Haidaia Crickmay 
Of the Harrison Lake species referred to this genus only one is typical. 
This form, related to H. dawsoni Whiteaves, is unluckily not represented 
by material good enough for specific description. The other three are 
new species which are referred to this genus for convenience, as it seems 
undesirable to make any further division until more forms are known. 
Haidaia sp. nov. aff. H. dawsoni Whiteaves 
Fragments of a new form, similar to dawsoni in the main but larger, 
longer in proportion to height, and having a narrower area. 
Locality. Southwest slope of Fossil hill at 1,850 feet; and on Billhook 
creek at 3,400 feet. 
Haidaia billhookensis sp. nov. 
Plate XII, figure 1 
Costae, numerous for a member of this genus. Tubercles, numerous, 
arranged in concentric series, degenerating toward basal margin. Costellae 
become irregular at maturity, rather resembling coarse growth lines. 
Marginal carina at maturity is a line of weak, irregularly spaced bullae. 
Median carina, lacking. Inner carina, not seen. Median furrow, shallow. 
Dimensions. Length, 77 mm.; height, 70; semidiameter, 25. 
Locality. Talus at 3,400 feet on Billhook creek. 
Name. After the locality. 
