6 
PALAEONTOLOGY OF NEW YORK. 
the Llandovery; L. Daphne, L. riciniformis, in the Trenton; L. Rouaulti, L. 
Hawkii, in the Budleigh-Salterton pebbles [Lower Silurian]; L. perovata, in the 
Clinton; L. cuneata, in the Medina sandstone; L. spatiosa, in the Lower 
Helderberg), diminishing during the Devonian ( L . Leana, in the Hamilton), 
and reaching the close of the Palaeozoic with a very meager representation 
(L. Scotica, L. flahellula, in the Carboniferous); and of the various types of 
outline, this is the only one not represented among living species of the 
genus. 
The generic’term Lingula, like many other names among the fossil brachi- 
opods, has long been a receptacle for various fossils, which, in the absence 
of knowledge of their internal characters, have been assumed to be con¬ 
generic. Recent observers have, however, made great progress toward a cor¬ 
rect understanding and limitation of the group. Many species of acuminate 
form originally referred to Lingula, have been found to differ so distinctively, 
in essential features, from the type species, L. anatina., that the erection of 
various other generic groups has been necessary; e.g., Lingulella, Salter, Lin- 
gulepis, Hall', Glossina, Phillips, etc. To some of these newer genera, probably 
belong most of the species from the primordial faunas, which have been 
described as “ Lingula,” a doubt resting upon all the species thus referred, 
whose interior markings are not known. Thus, L. ampla, Owen, L. Winona , and 
L. Mosia , Hall, from the Potsdam sandstone of Wisconsin, have the external 
characters of Lingula, and must, of necessity, be regarded as members of the 
genus, until the difference has been demonstrated from internal characters. 
Likewise, in the British primordial faunas are the species, L. squamosa, Holl, 
L. pygrnm, Salter, and L. petalon, Hicks, of which we have still to learn the 
true generic relations. The fact that as far as the internal characters of 
the species of the earliest faunas have become known they have shown generic 
differences from Lingula, may, to a certain degree, justify the temporary refer¬ 
ence of the species mentioned to some other group. 
This genus has been most remarkable for its wonderful adaptability to change 
in the conditions of life through immeasurable lengths of geological time, and, 
though in its strict limitation it may not have been represented in the earliest 
