INTRODUCTION 
TO THE 
STUDY OF THE GENERA OF THE PALAEOZOIC BRACHIOPODA. 
I. 
BRACHIOPODA IN A R T IC U L A T A. 
Valves inarticulated; intestine terminating in an anus on one side of the body; shell 
substance largely phosphatic. 
The foregoing characters bring into association a well defined assemblage of 
these organisms, but, while generally applicable throughout the group in ex¬ 
pressing the fundamental distinctions from the more abundantly developed 
Brachiopoda Articulata, there often appear, in forms which cannot be separated 
from such association, tendencies to transgress these limitations in various 
directions. For example, articulation of the valves was approached, if not 
effected, in the linguloid Barroisella, in Spondylobolus, and, perhaps also, in 
Neobolus and Trimerella. In Crania, according to the determination of 
Joubin,* the anus opens in the median line of the body; and in various genera, 
Cranta, Pholidops, Trimerella, etc., there is evidence that the substance of the 
shell was essentially, or altogether calcareous. 
We have preferred to adopt for this division of the Brachiopods, Professor 
Huxley’s-}- term, Inarticulata, which has the advantage of euphony and sim¬ 
plicity. Other writers have made use of terms with different significations, all 
* See under genus- Crania. 
t An Introduction to the Classification of Animals, p. 116. 1S69. 
