The ultrastructure of five common Pennsylvanian pleurotomarian gastropod species of eastern United States. American Museum novitates ; no. 2501

Supplemental Materials
Journal Title
Journal ISSN
Volume Title
New York, N.Y. : American Museum of Natural History
"The shell ultrastructure of five pleurotomarian gastropod species from the Pennsylvanian is described and and variation discussed; in addition, some observations are made of three bellerophontid species. Two thin outer shell layers previously unknown are analyzed. The outermost of these is fibrous and about 10 [microns] thick; it appears to be the only one that is actually involved in the topographic expression of growth. The two principal layers of the species studied are an outer complex prismatic layer and a thicker inner nacreous layer. There is an innermost complex prismatic unit which is variable in development and may be absent in some species. Several types of pallial myostracum are present in all species examined. The importance of shell structure in elucidating the origin and phylogeny of molluscan groups is briefly discussed. Most variation of ultrastructure appears to occur within or between species and is quite conservative between larger taxonomic units"--P. [1].
34 p. : ill. ; 24 cm.
Includes bibliographical references (p. 33-34).