398 
PALAEONTOLOGY OP NEW-YORK. 
These features are illustrated in the accompanying diagrams; fig. 1 being an oblique lateral 
view of the central portion of the spires, and fig. 2 a view of the same parts from the dorsal 
side.* * 
Meristella arccata. Meristella arcuata. 
In these figures, a indicates the origin of the crura; b the recurvation of the lamellae, 
which may be as represented, or with a simple retral -bending without recurving upon itself 
in some species; c is the continuation of the lamellae, which at d give off the processes 
forming the loop, and these become united at e and continue simple to f, where they bifurcate 
and continue in the direction g, returning again to the centre, and reuniting with the loop at 
A, or near the junction of the two parts before mentioned. 
These characters of the spires and loop have been observed in the M. la&vis , M. arcuata and 
M.princeps of the Lower Helderberg group, and in thg M. barrisi of the Hamilton group; 
while the M. nasuta presents a slight modification in the extension of the parts of the loop, 
which ally it more nearly with Athyris. 
"When compared with the spires of Athyris as shown in the figures already 
given under that genus, as well as the illustrations of Davidson and other authors, 
the differences are obvious. The parts of the loop in this genus, instead of curving 
forward and there uniting and turning backward and bifurcating, to form the 
accessary lamella, are continued from their origin obliquely backwards into the 
cavity of the ventral valve, and, then recurving upon themselves, are reunited 
laterally ; while in Athyris, they are intercalated between the first and second 
turns of the spire, and coalesce with the lamellfe of the latter. 
the generic name of Charionella ; professing to “ have ascertained the generic characters of the 
so-called Jltrypa or Mhyris scitula,” a species possessing the characters of Meristella, and none, 
so far a& known, which do not belong to that genus. He has subsequently united under the same name 
several other species of the latter genus. It is scarcely necessary to add that the characters of hinge, 
as described and illustrated in the dorsal valve of Charionella by Mr. Billings, do not exist in any 
species of this family (Spiriferidse) of Brachiopoda. 
* The words upwards and downwards, used in the descriptions of the spires in Athyris and 
Meristella, have reference to the position of the figures only, which are represented with the dorsal 
side below; since the illustrations could be more satisfactorily given in this position. ; 
