The Mode of Cladial Generation in Cyrtograptus

Abstract

The morphology of Cyrtograptus rigidus Tullberg n. subsp. A is described from uncompressed material. Particular attention is directed to the sequence of development of the connecting structure of cladium and main branch, which is demonstrated with the aid of figured growth stages of cleared and uncleared specimens. Also discussed is the intimate relationship of relative rate of growth of characters of cladium to those on the main branch. Cursory study of numerous other uncompressed species of Cyrtograptus in the author's collection reveals that the principles of cladial development outlined here are of general application.