Produced by The Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) $2.00 per Year. ($2.20 to Foreign 50 cts. a copy Countries.) THE NAUTILUS A QUARTERLY DEVOTED TO THE INTERESTS OF CONCHOLOGISTS EDITORS AND PUBLISHERS: H. A. PILSBRY, Special Curator of the Department of Mollusca, Academy of Natural Sciences, Philadelphia. C. W. JOHNSON, Curator of the Boston Society of Natural History. ═══════════════════════════════════════════════════════════════════════ Vol. XXXI. OCTOBER, 1917. No. 2 ═══════════════════════════════════════════════════════════════════════ CONTENTS: Notes on the variation of Ischnochiton conspicuus. By _E. P. Chace_ 37 Lampsilis ventricosa cohongoronta in the Potomac River. By _Wm. A. Marshall_ 40 Collecting about Guantanamo Bay, Cuba. By _John B. Henderson_ 41 Amnicolidæ from Oneida Lake, N. Y. By _H. A. Pilsbry_ 44 New Genera and Species of Central American Naiades. By _L. S. Frierson_ 47 On the rate of growth of pond Unios. By _L. S. Frierson_ 49 A new South African Nesopupa. By _H. A. Pilsbry_ 50 A new Gundlachia from Guatemala. By _Bryant Walker_ 51 A list of shells from the East Coast of Florida. By _Bryant Walker_ 53 Collecting in Digby, Nova Scotia. By _Lilian Dyer Thompson_ 57 A new type of the naiad-genus Fusconaia. By _A. E. Ortmann_ 58 The Relation of snail fauna to floods. By _A. Richards_ 64 William Bullock Clark 68 Publications received 69 Notes 71 ═══════════════════════════════════════════════════════════════════════ C. W. JOHNSON, Business Manager, Boston Society of Natural History, Berkeley Street, Boston, Mass. Entered as Second-Class matter at the Boston Post-Office. The Cruise of the “Tomas Barrera” By JOHN B. HENDERSON 32 full-page illustrations in black and white. 5 color plates. 5 maps. Octavo. $2.50 net.