LOCALIZED STAGES IN DEVELOPMENT. 153 



PENTA0RINC3 (ExTRACRINUS) BRIAREUS. 



Fig. 125. Showing dense association of cirrlii and pentagonal form of stem. Tliis pentagonal character is maintained 

 throughout the length of the stem in this species. XU. Jurassic. Enlarged. (Zittel, '76-'90.) P. 128. 

 Pig. 125a. Section of stem. (Zittel, '70-'90.) P. 128. 



Pentacrinus basaltiformis. 

 Fio-. 126. Showing strongly pentagonal form of stem. Jurassic. (Zittel, 76-'90.) P. 128. , 



Pl'ATYCRINUS SY.MMETRICnS. 



Fig. 127. Showing circular form of young plates of stem close to calyx and the change to oval form of plate in the older 

 part of stem. Subcarboniferous, Iowa. Xli (Wachsmuth and Springer, '97.) Fig. a, Section of stem close to calyx. Fig. 

 b, section further down the stem drawn from sui-f ace study. XlJ. P. 128. , 



Figs. 117-127 drawn by Mr. J. H. Emerton. 



Printed, April, 1899. 



