MERISTELLA OF THE UPPER IIELDERBERG GROUP. 
S99 
At tlie same time, an examination of the Niagara species referred by me to the 
Genus Meristella presents a different condition of the interior, and shows the 
lamellfe of the spires united by a simple loop only. 
This feature is illustrated in the accompanying diagram, which represents a single turn 
of the spiral lamellae, from their origin at a , to i where the bands are cut off. The thickened 
bases of the crura are represented at a; l is the point of recurvation, c the continuance of 
the lamellae in the dorsal cavity, and d the expansion on the inner side into long processes 
which unite at e, forming the loop.* 
Meristina maria ; 
Showing the first volution of the spiral lamellae. 
' The same characters have also been observed with equal distinctness in M. nitida of the 
Niagara group. In neither of these species is there any indication of accessary lamellae as in 
Athyris, nor evidence of the extension of the loop beyond the point e; and we are there- 
- fore induced to believe that the simple character of the spires in these forms will constitute 
another distinction, which may conveniently be termed Meristina. 
Meristella nasuta. 
PLATE XLVIII. 
Atrypa nasuta .- Conrad, Ann. Report on the Palaeontology of New-York, p. 18. 
Meristella nasuta ( Conrad sp.) : Hall, Thirteenth Report on the State Cabinet, p. 98. 1860. 
Meristella elissa : Hall, Fourteenth Report on the State Cabinet, p. 100. 1861. Fig. 21 & 22, Fif¬ 
teenth Report. 1862. 
Meristella nasuta : Hall, Fifteenth Report on the State Cabinet, p. 160 ; figs. 17-10, p. 161. 1862. 
Athyiis clara : Billings, Canadian Journal, p. 274. 1860. 
Athyris clara : Geology of Canada, p. 373, fig. 397. 1863. 
Shell suboval, ovate or subrhomboidal, the greatest width near or a little 
below the middle; the length equalling or greater than the width. 
Valves convex, the ventral valve gibbous. A nasute or linguiform 
extension of the front in old shells. 
# The point of junction in these parts varies in different species; and even in what appear to be the 
same species, the points of junction are not identical in all individuals. 
