908 Report or THE StaTE Gxroxocist. 
this point, it is important to first consider the basis of a classifi- 
cation and the significance of certain structural features. We 
have come, in our study of these creatures, very close to the point 
where any grouping of genera into families, or of these 
into broader divisions, is so palpably a violation of nature’s 
method as to make itself felt as an incumbrance. Hence 
the purpose of our treatment of these genera without such 
restrictions. Even among the generic groups there is so often an 
almost intangible transition from’one to another that the employ- 
ment of distinctive terms seems at times quite perfunctory ; but 
with the increase of such difficulties the nearer our classification 
may be regarded as approaching the true method of develop- 
ment. To us the genus represents a structural unit, a point of 
departure; species, diverse expressions of the generic type; 
families, associations of genera representing the offspring of 
common parentage. ‘ 
A classification is a broken and punctuated expression of 
organic affinities and interrelations, necessary to an easy treat- 
ment of any group of organisms, capable of expressing many 
truths in regard to the development of a race, but even in its 
most perfect state an index and confession of faulty knowledge. 
In the earlier classifications of the Brachiopoda a high value 
has been ascribed to the disposition of the muscular scars upon 
the inner surfaces of the valves, the form of the genito-vascular 
sinuses and the configuration and degree of calcification of the 
brachia. ‘To the last of these must still be ascribed a high degree 
of significance notwithstanding the fact that in the individual 
this calcification is a progressive process, increasing in extent 
from infancy to maturity. The plan of the muscular and 
vascular anatomy is, however, among the Articulate Brachiopods, 
but slightly modified through their history and in all their 
variations, but in the Inarticulate division we find it to be 
susceptible of a more varied expression. 
But it is the variation of form, position and mode of enclosure 
of the pedicle-passage that affords the most satisfactory index of 
lines of progress and development. We have already briefly 
referred to, and described the principal modifications of these 
parts, but a restatement of these structural details is essential to 
our purposes. 
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