LLUSTRATIONS. 
Bulletin No. 47. 
Page. 
Fig. 1. Apparatus for the estimation of carbonic acid 16 
2. Apparatus for the estimation of boric acid 18 
Bulletin No. 51. 
Plate I. Ostrea Dilleri 74 
II. Ostrea Dilleri 76 
III. Fulguraria Gabbi, Fulgur Hilgardi, -Trophon Condoni, Cancel- 
laria Turneri, Gyrodes Dowelli, Rimella macilenta, Ceratia 
nexilia 78 
IV. Scobinella Dilleri, Cominella LeContei, Mesalia obsuta, Trochus 
(Anadema) gemiferus, Stomatia obstricta, Faunus marcidulus, 
Lysis oppansus, Actseon inornatus, Vasculum obliquum, Zir- 
phsea plana 80 
V. Ammonites Turneri 82 
VI. Anatina sulcatina ?, Crassatella tuscana, Clisocolus dubius, C. 
cordatus 84 
VII. Perna excavata, Ammonites Maclurei, Vanikoropsis suciensis.. 86 
VIII. Teredo pugetensis 88 
IX. Batissa Newberryi, Cardium ?, Cerithium ? ? 90 
X. Sanguinolaria? caudata, Psammobia obscura, Cyrena brevidens, 
Neritina ?. .« 92 
XI. Batissa dubia, Corbicula Willisi, C. pugetensis 94 
XII. Ammonites Ho welli ' 96 
XIII. Ammonites Whiteavesi, Belemnites ?, A. kialagvikensis. .. 98 
XIV. Ammonites Howelli, Belemnites ?, Cucullaea increbescens, 
Glycimeris? Dalli ! 100 
Bulletin No. 52. 
Plate I. View of Mount Mitchell, North Carolina; looking north aloDg the 
crest of the Black Mountains. Roan Mountain in the distance. 16 
II. New Found Mountains; looking southwest from Asheville N. C. 20 
III. View of fields of residual clay, near Natural Bridge, Virginia; 
looking north. House Mountains in the background 26 
IV. Mayo River, North Carolina; illustrating the manner in which 
the rivers of the Piedmont region are eroding their beds. The 
rocks producing the rapids are Newark sandstones 31 
V. View from Harper's Ferry, W. Va., looking down the Potomac; to 
illustrate the manner in which the rivers of the Appalachians 
are eroding their beds 36 
v 
