PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 865 
gent sides. These usually have a moderately to broadly rounded anterior. The 
expanded front is a feature common to many of the specimens from the Little 
Oak limestone of Alabama. Some specimens from that formation are more 
expanded anteriorly than is usual in the variation of the species in Tennessee. 
Specimens referred to C. subquadrata from the lower Edinburg formation of 
Virginia are generally quite small and deep but appear to be well within the 
variation of the species. 
Some confusion has attended the identification of this genus and species in 
the United States by the fact that Hall and Clarke incorrectly stated its occur- 
rence as from the Helderberg formation of West Tennessee. These authors 
added to the confusion by failing to give any indication of the enlargement of 
their figures 32 and 33 on plate 15. On plate 15, figure 36, the enlargement of 
the posterior of the brachial interior is indicated as X3 whereas it is actually 
x4. The enlargement of the figures on plate 15 is about x 2. 
CHRISTIANIA TRENTONENSIS Ruedemann 
Plate 214, A, figures 1, 2 
Christiania trentonensis RUEDEMANN, New York State Mus. Bull. 49, p. 21, pl. 2, figs. 2-6, 
1901; Virginia Geol. Surv. Bull. 2A, pl. 3, figs. 14-16, 1900. 
This species has been widely identified in the Appalachians, but it is doubtful 
if any of the identifications are correct. The material on which this species was 
created is too poor to make any identifications with it a certainty. Ruedemann 
figures a specimen representing both valves. Examination of his figures and 
casts of the specimens indicates that all the figured specimens are actually brachial 
valves. Figures 2 and 3 of his plate 2 are stated to be respectively exterior and 
side views of the pedicle valve. Figure 2 is clearly a brachial valve as indicated 
by the straight and even hinge line. Furthermore, part of the shell is retained 
where it has not been exfoliated from the mold of the concave brachial exterior. 
In his description Ruedemann states: “Pedicle valve uniformly and strongly 
convex; umbo slightly projecting and very narrow, beak obscure.” Figure 2 
shows no slightly projecting umbo nor can it be seen in the cast. The profile 
view (fig. 3) is of the mold of the concave exterior which would have consider- 
able convexity. 
In connection with the brachial interior one point needs attention. This is 
Dr. Ruedemann’s description of denticles. No denticles such as he describes 
were seen in the extensive Appalachian material available for study. The casts 
of the types show several vertical lines and ridges, but these are located on the 
place from which the cardinal process has been torn. These are actually not 
denticles but represent the broken bases of the cardinal process. This feature is 
shown clearly in figure 6. Here the cardinal process narrows to points with the 
denticle on the outside. In well-preserved specimens the cardinal process con- 
sists of 2 moderately expanded lobes. 
Ruedemann prepared his specimens by roasting the limestone pebbles in which 
they occurred and then plunging them into cold water. This treatment naturally 
