226 
The American Geologist. 
October, 1901. 
lilirancliiatc life were not faltal at all to its continuance. Paii- 
citka and Liunilicardiiiin survived in both the ]\[arcellus and 
Genessee and Portage. 
If then the Marcellus, Genessee and Portage were marked 
by a diminished lamellibranchiate life, and if this diminution 
arose from the too strong prevalence of shore conditions ; 
floods, sufifusion of particles, dirtv water, brackish currents, 
sand-flats, tidal extremes etc., what does the general contin- 
uance of the lamellibranchs and their increase from the Upper 
Helderberg to the Waverly signify? 
Such a continuance in genera, as the following table shows 
is unmistakable. 
TABLE OF GENERA 
UPPER HEI.DERBERG 
Aviculopecten 
Conocardium 
Cypricaidinia 
Dystactella 
Glyptodesma 
HAMILTON 
Aviculopecten 
Actiiiopteria 
Allocardiurn 
Conocardium 
Cytherodon 
Cimitaria 
Cypricardinia 
Dvstactella 
Grammysia 
Lyriopecten 
Leiopteria 
Limoptera 
Mytilarca 
Modioniorplia 
Microdon 
Megambonia 
Nyassa 
Palaeopinna 
Pterinopecten 
Pterinea 
Panenka 
Paracyclas 
Elymella 
Glyptodesma 
Gosselettia 
Goniophora 
Grammysia 
Lyriopecten 
Leiopteria 
Leptodesma 
Limoptera 
Leda 
Lunulicardium 
Mytilarca 
Modiomorpha 
Microdon 
Modiella 
Macrodon 
Nucula 
Nuculites 
Nyassa 
Orthonota 
Pterinopecten 
Pterinea 
Panenka 
Paracyclas 
CHEMUNG 
Aviculopecten 
Actinopteria 
Conocardiam 
Cimitaria 
Cypricardinia 
Crenipecten 
Edmondia 
Ectenodesma 
Glossites 
Goniophora 
Grammysia 
Lyriopecten 
Leiopteria 
Leptodesma 
Lunulicardium 
Mytilarca 
Modiola 
Modiomorpha 
Microdon 
Macrodon 
Nucula 
Pterinopecten 
Pterinea 
Paracyclas 
