158 77/' Ann i-Kilii (t< iiliH/txt. s."i)t<'nil).'r, IS'.n 
The fauna of the Hamilton in middle Pennsylvania contains the 
following species : 
Brtiddoiiodn. 
Spirifera ziczac Hall. Strophodonta porplana Con. 
" mucronata Hall. Strophomena rhomboidalis Wahl. 
iiK'dialis Hall. Orthis pcnolqpe Hall, 
aonniiiiata Hall. Chonotos setijrcrus Hall, 
irranulifera Hall. " ooroiiatus Con. 
Rhynchonolla horsfordi Hall. Tro])idoleptus carinatus Hall, 
congrcgala Conrad. Atrypa reticularis L. 
Renssulipria sp. 
Ptcropodd. 
Tentaculites atlonuatiis Hall. 
Ldmcllihnnichiatii. 
Glypiodesraa rectum Con. Actinodesma subrectum Whit. 
Aviculopocten princcps Con. 
Gitstcroitmld. 
Loxonenia delphicola Hall. 
Ecliinodermatn. 
Ancyrocrinus bulbosus Hall. 
Cephalopoda. 
Nautilus liratus Hall. 
Crustacea. 
Phacops rana Green. Homalonotus delphinocephalus Green. 
W^rtchrata. 
Coccosteus ? 
Most of these fossils are forms which would be naturally looked 
for by the palieontologist in a middle Devonian formation. They 
characterize the Hamilton group of l^ennsylvania and adjoining 
states. But there are one or two on the list which are less famil- 
iar on this horizon and require a moment's notice. 
Rcnsschvria is one of those genera whose existence, even in- 
cluding its allied forms, Amphigenia and Newberria, is, so far as 
yet known, confined between the limits of the Lower Helderberg 
below and the Corniferous limestone above. Jienssehvria was es- 
tablished in 1859 by Prof. Hall to receive a number of peculiar 
shells of the type of R. ovoides. In 1867 one of these was re- 
moved by the author of the genus and made the type of the new 
genus Amphigenia. The range of these was as follows : 
Corniferous limestone Amphigenia elongata. 
llenssekeria johanni. 
Schoharie grit Amphigenia elongata. 
Oriskany sandstoiif Amphigenia curta. 
Rensselaer i a coiidoni. 
