Transcriber's Notes Mathematical Notation 1) _{#} for subscripted number or character and ^{#} for superscripted number or character Example: Carbonate Ion = CO_{3}^{--} 2) Whole and fractional number: 7-2/3 Text Emphasis Italic words displayed as _Text_ and bold as =Text=. UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 13, No. 10, pp. 429-611, pls. 31-54, 24 figs. February 16, 1962 North American Recent Soft-shelled Turtles (Family Trionychidae) BY ROBERT G. WEBB UNIVERSITY OF KANSAS LAWRENCE 1962 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 13, No. 10, pp. 429-611, pls. 31-54, 24 figs. Published February 16, 1962 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1962 [Illustration (Union Label)] 28-7818 North American Recent Soft-shelled Turtles (Family Trionychidae) BY ROBERT G. WEBB CONTENTS PAGE CONTENTS 431 INTRODUCTION 433 Collecting Methods 434 Materials and Procedure 437 Acknowledgments 439 TAXONOMY 439 Family Trionychidae Bell, 1828 439 Genus _Trionyx_ Geoffroy, 1809 443 Variation 445 Secondary Sexual Variation 446 Ontogenetic Variation 449 Geographic Variation 453 Character Analysis 460 Composition of the Genus _Trionyx_ in North America 476 Artificial Key to North American Species and Subspecies of the Genus _Trionyx_ 476 Systematic Account of Species and Subspecies 479 _Trionyx ferox_ 479 _Trionyx spinifer_ 486 _Trionyx spinifer spinifer_ 489 _Trionyx spinifer hartwegi_ 497 _Trionyx spinifer asper_ 502 _Trionyx spinifer emoryi_ 510 _Trionyx spinifer guadalupensis_ 517 _Trionyx spinifer pallidus_ 522 _Trionyx ater_ 528