Urbanek, Adam. <br/><br/>
Ultrastructural studies on graptolites / 
Adam Urbanek and Kenneth M. Towe. 
 - Washington :  Smithsonian Institution Press,  1974. 
 - 2 v.:  ill. ;  27 cm. 
 - Smithsonian contributions to paleobiology  n.20 .
<br/><br/>Includes bibliographies. 
<br/><br/>1. The periderm and its derivatives in the Dendroidea and in Mastigograptus.--2. The periderm and its derivatives in the Graptoloidea. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Graptolites.<br/>Paleontology--Ordovician.