BRACHIOPODA. 
61 
fauna of Square Lake, Maine. Of the foregoing species we know the character 
of the loop in Whitjieldella cylindrica, W. nitida and W. intermedia. 
The forms of Whitfieldella cylindrica occurring in the Niagara limestone at 
Hillsboro, Ohio, have a remarkably elongate shape, broad and abrupt cardinal 
slopes on the pedicle-valve, subnasute anterior extremity. In these respects 
the species differs from other members of the group, but the character of its 
loop as developed from a solid internal cast in silica, requires, for the present, 
its retention in this association. 
A very similar species in all external characters is Dalman’s Alrypa prunum, 
from an equivalent liorizon in Gotland 
Genus HYATT ELLA, gen. nov. 
PLATE XLVIII. 
This term is introduced for a group represented by the peculiar species, 
Atrypa congesta, Conrad, of the fauna of the Clinton group. 
This species has been found to possess a loop like 
that of Whitfieldella, but presents some significant 
points of variation from that genus in other re¬ 
spects, viz. : 
Fig. 45. The loop of Hyattella 
The form is compactly subpentahedral; the umbo congesta, iiaii. (c.) 
of the pedicle-valve acute, concealing most of the deltidium. The pedicle- 
valve bears a strong median sinus and two faint lateral sinuses, the opposite 
valve having corresponding folds. The surface of the shell and the ante-lateral 
margins are strikingly sinuate. Fine, sharp, closely crowded concentric strim 
cover the exterior. The interior of the pedicle-valve has a deep and strongly 
striate pedicle-cavity, bounded by strong dental lamellae ; the diductor scars 
are distinctly defined, enclosing a linear adductor. In the brachial valve the 
hinge-plate is triangular and divided medially by a deep cleft. The lateral 
portions are broad and elevated, supporting short, straight crura. The spiral 
ribbon makes not more than six- volutions, forming very loose coils. There 
is no median septum. 
