ADDENDA. 
48 3 
From the external character of the species referred by me to Atrypa aprinis , 
Palseont. New-York, Yol. ii, pa. 280, pi. 57, f. 7 ( = Terebratula aprinis , M. Y. K. 
Geol. Russia and the Ural Mountains, Yol. ii, pa. 90, pi. x, f. 10), I infer that it 
belongs to this genus, and the name Rhynchospira apriniformis may be adopted for 
it, since the American find European forms are probably distinct. 
Rhynchospira form os a. 
Plate XCY A. Fig. 7 - 11. 
Fig. 7. Interior of the ventral valve of Rhynchospira formosa. 
Fig. 8. Interior of the dorsal valve, enlarged two diameters, to show the broad cardinal 
process (j), which covers the extremity of the beak, and, when the valves are 
closed, passes beneath the deltidial area of the opposite valve. The bases of the 
crura ( c ) are shown on each side at the base of the cardinal process, and the 
short median septum is shown at s. 
Fig. 9. Profile view of the same, showing the cardinal and crural processes. 
Fig. 10. The upper part of the two valves connected in their natural relations to each other, 
and showing the manner of articulation. 
Fig. 11. A longitudinal section, showing the foramen, the deltidium, and the cardinal process 
of the opposite valve lying beneath it ; the crura first bending downwards, and 
then recurved into the dorsal valve and its continuation in the spire, with the 
descending process e, which forms, with the opposite one, a connecting filament 
between the two spires. 
Rhynchospira rectirostra (page 217). 
Plate XCY A. Fig. 1 a, 6, c. ( These figures are referred, at page 217, to 
Plate xxxvi A, fig. 1 a , b, c.) 
CAMARIUM. 
Among the fossils referred by me to the Genus Merista, and published 
in the Report of the Regents of the University in 1856 and 1857, and 
printed in this volume in the year last mentioned, are several, which, 
although possessing the general form of Merista , present nevertheless 
some noticeable peculiarities. One of these is the strongly incurved beak 
of the ventral valve, while the cardinal margin is abruptly bent inwards, 
leaving an angular or subangular ridge extending from the beak to the 
margin of the shell, the space between this and the cardinal margin being 
sometimes flattened about halfway to the base. The front of the shell is 
often produced in a broad linguiform extension of the ventral valve : 
