No. 466.] NOTES AND LITERATURE. 755 
tion took place (which I doubt very much) by what law of nature 
could the plates twist themselves from the position indicated in fig. 
11, pl. 3, to that shown in fig. ro, pl. 3?" A more careful reading 
of their explanation of the figures would show that tbe plates would 
not by any law of nature necessarily have to twist themselves in any 
way, as it is stated that figure 11 is adapted from one specimen, 
while figure 10 is drawn from an entirely different specimen which 
is described as aberrant. 
In regard to the idea of the introduction of columns there is an 
entire misunderstanding of the statements of Jackson and Jaggar. 
They call the two columns which terminate at the ventral border, 
columns ı and 2, then the next added column is spoken of as the 
third column, etc. Miss Klem does not make this grouping but 
makes one of her own, in which the early columns are ignored and 
the first column in her scheme is the first one added above the bor- 
der shown in her figures. "Therefore the first column of her scheme 
may correspond to the third, sixth, or any column of the other au- 
thors except what they really call the first. With such a failure to 
use equivalent terms it is obvious that other results are obtained 
especially in a group where the structure is largely one of numerical 
sequence. As a result of this difference in terminology, the follow- 
ing statement is made: “While this rule (‘that.... newly added 
columns normally alternate to left and right as introduced, even 
numbered columns typically appearing on the right of odd ones’) 
may apply to some isolated and imperfect. specimens, the contrary 
becomes quite evident by examining a large and complete collection 
of perfect fossils." Twenty-three figures are referred to in order to 
show that the rule does not hold in usual cases. However, by using 
the basis of numbering given by the original authors at least seven- 
teen out of these twenty-three figures given by her show decidedly 
the correctness of their rule. 
A statement which needs correction is given on page 5: “An- 
other feature, which will not stand a critical test, is the supposition 
of the above mentioned authors, that new columns are always intro- 
duced by a pentagonal plate with the apex pointing ventrally or 
toward the oral area." Exceptions are given to the rule but the fact 
is overlooked that the original authors show that there are excep- 
tions, as in figure ro where a column is introduced by a tetragonal 
plate, in figure 14 where one is introduced by a hexagonal plate, and 
in figure 16, where one is introduced by a heptagonal plate, the same 
variations that Miss Klem simply reiterates. The statement is made 
that “the initial plate of a column when pentagonal often has the 
