676 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
74mm. wide, 65 mm. long, and 44 mm. thick. The pedicle valve bears a marked 
fold that extends from the umbo to the anterior margin. The brachial valve is 
deeply sulcate but is without a fold in the sulcus as is usual in the zygospiroids 
under study. The lateral margins are narrowly convex and the anterior margin 
is excavated medially. The beak is broken off so that the foramen and delthyrial 
region are not available, although the figures of the specimen reproduced by 
Hall and Clarke show a small circular foramen which is totally unlike that of 
any of the zygospiroids in question. The most surprising feature of this speci- 
men is its finely punctate shell. Internally, little can be seen, but the beak is 
broken off in such a way that dental plates would be revealed if the specimen 
had had such structures. The form of the specimen, its lack of dental plates, and 
its punctate shell, as well as its fresh appearance, indicate a specimen far younger 
in age than any of the zygospiroid stock. The ensemble of characters suggests 
one of the terebratuloids with fold on the pedicle valve of the Mesozoic such as 
Nucleata, Pygope. How such a specimen could be confused with Airypa exigua 
from New York can only be conjectured, but its equivocal nature excludes it as 
a holotype for the species. The remaining three specimens are available for 
choosing a lectotype. Of these three, the one from Watertown, New York, is 
rejected as not belonging in the original lot. Of the remaining two, one is im- 
mature and without costae, the other is imperfect, having a small sliver out of 
one side. This specimen is adult in size and exhibits the costae faintly. It is 
therefore selected as type of the species. 
Protozyga is a fairly common genus in the rocks covered by this monograph. 
It occurs first in the Crown Point limestone from which a single specimen is 
known. This specimen is an elongate form with prominent attenuate beak and 
a few obscure costae on the margins. The interior of this specimen is unknown, 
but it is the earliest brachiopod like Protozyga to be seen. 
In the Southern Appalachians the genus appears first in the Whistle Creek 
formation, but the three specimens taken do not yield information on the interior. 
These specimens are not folded like the later ones, which might be a natural 
characteristic of one of the earliest members of the genus. 
Specimens are locally abundant in the Ward Cove limestone and the Benbolt 
and Wardell formations. In these the tendency to folding is more highly de- 
veloped, but this reaches its maximum development in Trenton species. The 
Rockland formation yields P. exigua which is strongly folded and fairly strongly 
costate. The folding reaches its maximum in P. profunda. 
PROTOZYGA COSTATA Cooper, new species 
Plate 142, A, figures 1-5 
Small, oval in outline with the length greater than the width; widest at the 
middle ; valves unequal, the pedicle valve having a greater depth than the brachial 
valve; apical angle 100° ; sides rounded; anterior margin rounded to subnasute ; 
anterior commissure faintly sulcate ; surface paucicostate, 2 costae in the sulcus 
(rarely 3), 3 costae on the fold (rarely 4), and 4 costae on the flanks ; costae 
usually not extending for more than two-thirds the length from the margin. 
