BRACHIOPODA. 
67 
consists of two lateral branches, broad at their origin, inclined backward, and 
uniting to form a stem which bears a short bifurcation at its extremity. 
The muscular area is elongate-ovate and more or less distinctly separated 
into anterior and posterior scars. Surface of the valves smooth or with fine 
concentric growth-strim. Shell-substance fibrous, impunctate. 
Type, Meristella Maria, Hall. Niagara group. 
Observations. The name Meristina, proposed in Volume IV of the Palaeon¬ 
tology of New York (p. ‘.^99), was introduced for the purpose of distinguishing 
from Meristella a species, M. Maria, Hall, which possesses strong meristelloid 
characters but lacks the peculiar loop of that genus. Though the loop was im¬ 
perfectly represented in the figure accompanying the first use of the name, it 
nevertheless constituted then, as it still does, the single important difference of 
the species from Meristella. The precise character of this loop was fully 
determined subsequently (as described and illustrated in the present work), by 
the Rev. Norman Glass, from specimens obtained at the celebrated locality, 
Waldron, Indiana,* and described by Dr. Davidson in 1882.f Mr. Glass found 
a loop of like structure in the English (Wenlock) examples of the Atrypa turnida, 
Dalman. In the place cited Dr. Davidson expresses his conviction of the 
identity of the American species M. Maria with Atrypa turnida, and as the form 
of the loop then determined was new, he proposed to distinguish these fossils 
by the generic name Whitfieldia. 
It is to be regretted that the laws of nomenclature do not permit the 
admission of this name. Whether or not Dalman’s species and the American 
M. Maria be conspecific, :j: they are at all events congeneric, and belong to the 
much earlier genus, Meristina. That this genus was imperfectly described 
* Though this species is a rare fossil in the Niagara fauna of New York, it is very abundant at Waldron 
and far from infrequent in the Niagara dolomites of northern Illinois and southern Wisconsin. 
t Silurian Supplement, p. 108, pi. v, fig. 6. 
J We do not follow Mr. Davidson in regarding these forms identical. They present differences which 
though slight, are positive and permanent variations of the same type of structure. A series of Gotland 
specimens of Atrypa turnida, obtained from, and identified by Dr. Lindstrom, and submitted for our exami¬ 
nation by Mr. Charles Schdcuert, shows that there are two readily apparent variations in the forms refer¬ 
red to the Swedish species, and it is an interesting fact that these are from different localities. One of these 
forms (fi'om Westergarn) is of small size, strikingly subpentagonal outline, with high, strongly arched and 
narrow umbo on the pedicle-valve, the greatest diameter of the shell being |in front of the middle; while 
