90 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL, XXXIV, 
It is also represented in America by the common Hamilton form 
Pterinea flabella Conrad. 
It was recognized by Frech under the heading “ gruppe der 
Pterinea costata.” That species while holding the generic characters 
is more extreme and less typical of the generic characters than 
P. fasciculata, which is here taken as the generic type. | 
The genus as defined is not certainly known to appear in the Maine 
rocks. Clarke has described a small species from Presque Isle Stream, 
under the name Pterinea cf. fasciculata Goldfuss, and others from 
Dalhousie, New Brunswick, under the name Pterinea fasciculata 
Goldfuss, var. occidentale, but both of those forms have the right 
valve convex, whereas in the right valve of Cornellites (as in Pterinea 
sensu stricto, Micropteria, Follmannella, and Tolmaia) the right 
valve, while shehtly convex at the umbonal end, rapidly flattens and 
before reaching the ventral margin in adult shells becomes resupinate. 
In North America Cornellites (Pterinea) flabella Conrad is a repre- 
sentative species of this genus and it is often abundant in the Hamiul- 
ton rocks of New York State. - 
In this paper no attempt is made to go beyond the set of forms 
included by Goldfuss in his genus Pterinea. Of the accepted Pteri- 
neas, those of the type P. dwvis, normally without radial surface 
sculpture, constitute the genus Pterinea Goldfuss sensu stricto. 
The species of type of P. ventricosa, without radial surface sculp- 
ture, are mentioned under the name J/icropteria Frech. ‘The species 
with fine radial sculpture of types of P. lineata Goldfuss are called 
Tolmaia; forms resembling 7’ol/maia in sculpture, but having bicon- 
vex shells, probably including P. lamellosa and P. reticulata are as- 
signed to a new genus Actinopterella. Other forms of similar surface 
markings but with large shells and curved body, the ventral portion 
extending backward beyond the extreme end of wing, like Frech’s 
P. ostreiformis in form, are called Follmannella, new genus; and 
finally the species of type P. fasciculata and represented in America 
by Pterinea flabella are called Cornellites, new genus. 
In the preparation of this paper the valuable assistance of Mr. C. L. 
Breger is hereby acknowledged. He has thoroughly reviewed the 
literature bearing upon the subject and worked over the materials 
with the author, making several important suggestions. The author, 
however, is responsible for the classification and descriptions here 
given. 
