1<>2 The America)! Geologist. Febraarj-. 1894 
A REVISED CLASSIFICATION OF THE SPIRE- 
BEARING BRACHIOPODA. 
By Charles Schuchert, Washington, D. C. 
Iii the March number of the American Geologist for 1893, 
the writer published a paper entitled "A Classification of the 
Brachiopoda." Several works on the spire- bearing brachiopods 
have since appeared,* which greatly increase the knowledge 
of the suborder Helicopegmata, and suggest a more natural 
classification than was then possible. Therefore the following 
revised classification is offered: 
Fa mil [i Characters. Three types of brachidial structure of 
family importance have been observed which will serve to 
characterize the three families into which the suborder Heli- 
copegmata is here divided. These structures are based on the 
position of the primary lamellae with reference to the spirals 
and to the manner in which they join with the crura. These 
characters are as follows: 
1. In the earliest and most primitive forms, the Atrypidas, 
the primary lamellae are directly continuous with the crura. 
diverge widely and have the spirals between them. 
2. In the Spiriferida:, the primary lamellae are also directly 
continuous with the crura, but lie between the spirals, thus 
being the reverse of the Atrypida . 
3. In the Athyridm the primary lamellae differ in direction 
from those in the other families in being more or less sharply 
recurved dorsally near their junction with the crura. 
Subfamily characters. The nature and complexity of the 
loop which joins the spirals is the most important character 
for subfamily differentiation. There are five types of loops, 
the greatest variety occurring in the Athyridm. Two of these 
are restricted, being common to the A.trypidai and Spiriferidas, 
while the three pertaining to the Athyridai are specializations 
* James Hall, assisted by John M. Clarke. An Introduction to the 
Study of the Genera of the Pala?ozoic Brachiopoda, Pal. New York, vol. 
viii, pt. ii, fascicle i, pp. 1-176, July, 1893. 
A. Bittner. Bracbiopoden der Alpinen Trias, Abb. d. k. k. geol. 
Reichs., Bd. xiv, pp. 1-325, Taf. 1-41, 1890; Nachtrag I, Ibid., Bd. xvii, 
Heft 2, pp. 140, Taf. 1-1, 1892; Neue Koninckiniden des Alpinen Lias, 
Jahrb. d. k. k. geol. Reichs., Bd. 43, Heft 1, pp. 133-144, Taf. iv, 1893. 
C. E. Beecher and C. Schuchert. Development of the brachial sup- 
ports in Dielasma and Zygospira, Proc. Biol. Soc. Washington, vol. viii, 
pp. 71-82, 1893. 
