10 
K. L. PRENDERGAST. 
It was accepted thus by Waagen (1884, p. 611) who said: — 
“the most striking- character is the existence of reniform prominent 
ridges on the inside of the dorsal valve, a character which in this 
strong and distinct development, is entirely restricted to the 
Productidae.^' 
Waagen subdivided the forms so characterised into two sub-families, 
Chonetinae and Productinae. 
The Chonetinae were characterised by the presence of teeth and a car- 
dinal area in the pedicle valve and of non-dendi’itic muscle impressions. This 
sub-family included the genera Chonetes^ Strophalosia^ Chonetella and 
Daviesiella, Most of these forms are free. 
The Productinae were defined as Productids in which the pedicle valve 
is without cardinal teeth and the adductor muscle impressions are dendritic. 
Some of the forms are fastened by the entire pedicle valve or by spines. 
Waagen placed the genera Aulosteges, Productella, Productus and Margini- 
fera in this sub-family. 
Schuchert (1913, p. 389) changed the emphasis in King's diagnosis 
and defined the Productidae as “Strophomenacea with hollow anchoring 
spines." 
Schuchert also altered the content of the sub-families by using the means 
of attachment of the shell as the main diagnostic feature. Thus the 
Chonetinae became 
“Productids with a few anchoring spines restricted to the ventral 
cardinal margin," 
and the Productinae 
“Productids with the anchoring spines more or less abundant over 
the entire ventral and sometimes also over the dorsal valve," 
while he founded a new sub-family the Strophalosiinae to include 
“Productids anchored to foreign objects by spines or by most of the 
ventral shell.” 
Such a division of the Productidae is purely arbitrary and while it groups 
together forms superficially alike, makes no allowance for a similarity of 
external form due to growth under similar environmental conditions. The 
sub-familv Strophalosiinae^ for example, includes the genera Chonopecttis^ 
Strophalosia, Aulosteges and Etheridgina. 
Strophalosia King, the type genus of the sub-family is an attached 
form, being cemented by the umbo of the pedicle valve and/or by spines. It 
has a welf-developed area on each valve, non-dendritic muscle impressions 
.-and strong teeth. Etheridgina possesses an area only on the pedicle valve, 
teeth may be developed and the shell is cemented directly by part or the 
whole of^the pedicle valve and by spines. The muscle impressions are as in 
Strophalosia. 
The genus Chonopectus Hall and Clarke is represented by a single 
species Chonopectus fisheri Norwood and Pratten from the English River 
beds of the Kinderhookian (equivalent to K beds. Lower Carboniferous) of 
Burlington, Iowa, U.S.A. This species is essentially a small Chonetes with 
a distinctive ornamentation and attached at some period during its life 
history. It is a restricted form, both geologically and geographically. 
