Twenhofel, William H.  1875-1957. <br/><br/>
Principles of invertebrate paleontology / 
by Robert R. Shrock and William H. Twenhofel. 
 - 2d ed. 
 - New York :  McGraw-Hill,  1953. 
 - 816 p. :  ill. ;  24 cm. 
<br/><br/> 'A revised and enlarged edition of Twenhofel and Shrock, Invertebrate paleontology.' 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Invertebrates, Fossil.