PLATE 42. 
Legend. dp. Dental plates. VA. Cardinal area. 
A Delthyrium. pm. Pedicle-muscle. 
s. Median septum. a. Adductor scars. 
t. Teeth. r. Diductor scars. 
ce. Crural bases. 
RHYNCHONELLA, Fisonzr pz WatpHEIm. 
Page 823. 
RHYNCHONELLA Loxta, Fischer de Waldheim. 
Figs, 1, 2. Anterior and profile views of a normal mature individual, retaining 
the smooth external surface, and showing the contour of the shell. 
Fig 3. Cardinal view of an internal cast; showing the cavity of the dental 
plates and median septum. 
This is the type of the genus RHYNCHONELLA. 
Upper Jurassic. Charaschowa, Russia. 
PROTORHY NCHA, Hatt. 
Page 824. 
PROTORHYNCHA HQuIRADIATA, Hall. 
Fig. 4, An internal cast of a larger pedicle-valve; showing a well defined 
median sinus and a very restricted muscular scar in the umbonal 
region, X 2. 
Fig. 5. An internal cast of the brachial valve; showing the length of the 
median septum. 2. 
Fig. 6. The cardinal portion of the brachial valve enlarged; showing a clearly 
defined cardinal area, oblique dental sockets, the broad, rather ill- 
defined hinge-plate, with a median cavity whose lateral walls are 
continuous with the median septum. ~* 3. 
Clinton group. New Hartford, N. Y. 
ORTHORYNCHULA, Hatt. 
Page 824. 
OrtHoguyNcHULA Linneyi, Nettelroth. 
Figs. 7-9. Dorsal, ventral and profile views of the exterior of an average 
example; showing contour and character of plication. 
Fig. 10. The central portion of the cardinal region, enlarged; showing the 
sharply defined cardinal area and the opendelthyrium. X 3. 
Hudson River group. Nashville, Tennessee. 
239 
