620 
Pl, ili, They are somewhat enlarged and show the loose coiling of several genera 
in the nepionic stages of development during this period of their evolution. Sub- 
sequently the coiling becomes closer, as has been demonstrated by Branco. Fig. 
20, Mimoceras compressum ; Fig. 21, Anarcestes subnautilinus ; Fig. 22, Agonia- 
tites bicanaliculatus, var. gracilis; Fig. 23, Gephuroceras planorbe, Fig. 24, 
caleuliforme, and Fig. 25, sublamellosum; Fig. 26, Manticoceras latidorsale, 
and Fig. 27, Glyphioceras diadema. 
Figs. 28 and 29. Protoconch of Orthoceras, after Clarke, Az. Geol., xii, 
August, 1893. 
Figs. 30 and 31. Protoconch of Bactrites, after Branco. 
