962 



SCIENCE. 



[N. S. Vol. TV. No. 104. 



Mr. Calkins reported on the protozoa and 

 coelenterates of Puget Sound and of the 

 Alaskan Bays. The protozoa and coelenterates 

 collected during the summer by Mr. Calkins 

 belong chiefly to the group flagellata for the 

 former, and to the leptomedusse for the latter. 

 In addition, there are two species of hydroids — 

 a large number considering the very limited 

 representation of this group in the western 

 waters. Twelve or fourteen species of actin- 

 ians and about the same number of sponges, 

 and several scyphomedusse complete the list 

 of coelenterates. 



Dr. Bashford Dean reported on the chor- 

 dates and protochordates of the collection. 

 The ascidians are represented by about a 

 species, fishes by upwards of forty. The 

 most important part of his work had been the 

 collecting of embryos and larvae of Chimsera 

 (Sydrolagus colliei) and a fairly complete 

 series of embryos of Bdellostoma, including 

 upwards of twenty stages from cleavage to 

 hatching. Of Chimsera upward of eighty egg 

 cases had been dredged in a single day ; but in 

 every case these were found to be empty. The 

 eggs were finally obtained at Pacific Grove, 

 California, from the gravid females and were 

 incubated in submerged cages. It was in this 

 locality that the eggs of Bdellostoma were col- 

 lected. C. L. Bristol, 



Secretary. 



GEOLOGICAL SOCIETY OF WASHINGTON. 



At the 53d meeting, held in Washington, 

 D. C, December 9, 1896, Mr. Whitman Cross 

 gave an account of some unusually large land- 

 slides observed in the Telluride region of Col- 

 orado. The slides occur on the western face of 

 the San Juan Mountains, where the San Miguel 

 conglomerate and a thick series of volcanic 

 beds rest upon Cretaceous shales. Water per- 

 colating through the upper beds has softened 

 the shales and caused the slides. 



It is clear that the slides occurred long ago 

 when the topography of the mountain front 

 was even more rugged than at present. Masses 

 of rock two miles in length and more than 

 1500 feet in vertical dimension have slipped, 

 apparently as a unit, for several hundred feet. 

 In such cases the bedding of the mass dips to- 



ward the mountain from which it was detached. 

 Subsequent slides of portions of the original 

 mass have greatly modified the relationships of 

 the rocks. 



Mr, W J McGee detailed certain observa- 

 vations on ' The Formation of Arkose. ' The 

 region in which the process was observed is the 

 eastern shore of the Gulf of California or the west- 

 ern coast of the State of Sonora, Mexico, about 

 latitude 29°. The region is one of broad plains, 

 base-leveled by sheetflood erosion, these plains 

 being relieved by notably rugged mesas and 

 sierras. The rocks consist largely of granites 

 and granitoid schists, evidently of considerable 

 antiquity, together with considerable beds of 

 igneous rocks, tuffs, etc., probably ranging from 

 Mesozoic to middle Tertiary in age ; in the 

 mesas and sierras the rocks are practically bare, 

 while in the flood-sweep plains they are ve- 

 neered with a thin sheet of coarse alluvium, 

 ranging from a few inches to a few yards in 

 thickness, which becomes fine and of consider- 

 able thickness only in the axes of the greater 

 valley plains. Between Puerto Infierno and 

 Punta Ygnacio (mapped in National Geographic 

 Magazine, Volume VII., 1896, plate xiv.) the gulf 

 shore reveals a section of rocks and overlying 

 mantle in a range of sea cliffs, averaging 30 or 

 40 feet in height between the lower ranges 

 which jut into the gulf in such manner as to 

 form prominent points ; while the shore is 

 skirted by a wave-cut bench or terrace lying 

 slightly below extreme low tide, averaging 

 some 100 yards in width, beyond which the 

 gulf deepens rapidly. The prevailing rocks are 

 slightly schistoid granites, while the alluvial 

 veneer is composed chiefly of granitic products. 

 The region is one of high tides and strong tidal 

 currents, and is subject to strong winds, rising 

 almost daily into gales, induced by general cli- 

 matic and local topographic conditions ; the 

 climate is notably arid, and no fresh waters 

 ever flow into the gulf save locally and for a 

 few hours after the greatest storms. In the 

 course of a visit to the coast in December, 1895, 

 the speaker observed the rapid work of the waves 

 in sapping the cliffs during a gale ; and on one 

 occasion, at low tide with an off'-shore wind, he 

 passed well toward the outer margin of the 

 wave-cut terrace, examining the debris accu- 



