ACADEMY OF NATURAL SCIENCES. 339 



XVII Group. Aplodon Raf. One parietal tooth, (or none) perfo- 

 rate or imperforate, hirsute or smooth, lip simple. 



52 Columbiana Lea. Wh. 5)4 to 6, corneous brown, with or without 

 hairs, umbilicate ; diam. 0.50 to 0.70, axis 0.25 to 0.35. The small imperforate 

 and toothed form usually classed with this species may better be considered a 

 rounded var. of germana, the subangled form of which is very rare. 



53 germana GUI. " Wh. b%, reddish corneous, hirsute, subangled, one 

 parietal tooth, imperforate ;" diam. *0.30, axis 0.20. 



XVIII Group. Triodopsis Raf " Umbil. large, a tooth on each 

 lip, and one parietal." Sometimes hirsute, hairs deciduous. 



54 Mullani Bid. Wh. b% to 6, brownish corneous, microscopic spiral 

 lines and tubercles ; (hairy ?) diameter *0.53, axis 0.29. 



55 lorieata Gld. Wh. 5)^, brown or greenish, scale-like wrinkles quiu- 

 cuncially arranged ; diam. *0.25 to 0.35, axis *0.10 to 0.20. 



I am indebted to Dr. Newcomb and Mr. K. E. C. Stearns for much assist- 

 ance in preparing this paper. Though not offered as a final arrangement of 

 the species, it is hoped that this synopsis may aid in their determination, and 

 thus make a step towards a correct systematizing of this difficult series. 



There are four or five other subgenera among the 50 species of this family 

 in the Atlantic States, divided by Bland into fifteen groups. He places Nos. 

 51, 54, and 53 in his 8th, 9th, and 15th groups respectively. — (Ann. N. Y. Lye. 

 N. H. 1864.) 



Prof. W. P. Blake read the following : 



Origin of the Submerged Forests in the Columbia River, 



Oregon. 



BY WM. P. BLAKE. 



The submerged forests of fir trees, extending about twenty-five miles along 

 the Columbia River, above the Cascades, have long excited the curiosity of 

 travelers upon that stream. The trees stand erect as they grew, but the tops 

 have decayed and broken off, leaving only those portions of the trees that have 

 been protected from the air by the covering of water. At extreme high-water 

 very few of these old trunks can be seen, but at low-water they appear in great 

 numbers, and project a few inches or feet above the surface, and in some places 

 they extend far out into the stream. 



These trees are not petrified, as is supposed by many. The outer portions 

 are much softened and partly decayed, but towards the heart the wood is sound, 

 and appears to be identical in character with the fir which covers the mountains 

 around. Some cedar stumps are also found. 



It is well known that fir trees will not grow below the high-water mark of 

 our streams, or where the roots would be subject to overflows. Flooding the 

 roots of the fir even for a few days is sufficient to destroy its life. It is thus 



