Principles of invertebrate paleontology / Robert R. Shrock [and] William H. Twenhofel. Invertebrate paleontology. Twenhofel, William H. (William Henry), 1875-1957. Shrock, Robert R. (Robert Rakes), 1904-1993, joint author. Invertebrates, Fossil. QE770 .T8 1953 562 SHP Includes bibliographical references and index. New York : McGraw-Hill, 1953. 1953. 1953 Text xx, 816 p. : eng McGraw-Hill series in geology