PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 137 
i 
a bilobed cardinal process necessary to produce the leptaenoids. The family re- 
tained its pedicle opening through all the time embraced by this monograph. 
DALMANELLACEA.—The earliest known punctate brachiopod on this continent 
is Paurorthis, which is found in rocks formed during the Ashby stage. The genus 
has some features that relate it to the Orthidae, such as the form of the vascula 
media and the nature of the brachiophores. It seems difficult, however, to derive 
other punctate forms from this one. 
Several other punctate stocks appear simultaneously in the Porterfield stage: 
Cyclomyonia, Paucicrura, and Laticrura. The first-named has the structure of 
Pionodema and the Schizophoriidae. It seems to form a satisfactory originating 
point for that family, but the stock from which Cyclomyonia itself came cannot 
be conjectured. Paucicrura may have been derived from Paurorthts. This seems 
possible, but it cannot be accepted with assurance. With Paucicrura came the 
large family of Onniellidae which has a greater development in Europe than in 
America. Laticrura parallels Scaphorthis in its cardinalia, and no progenitor is 
known for it. The Heterorthidae appear to have had their origin outside of 
America, possibly in the Llandeilo of Great Britain. Elasmothyris appears to be 
a complicated punctate brachiopod but is probably out of the main line. 
