THE 
AMERICAN GEOLOGIST 
Vol. VII. MAY, 1891. No. 5. 
A CHART OF THE RUGOSE CORALS. 
Will H. Sherzer, Ann Arbor, Mich. 
For the student who endeavors to acquire anything more than a 
superficial knowledge of a few of the more common genera of 
Palaeozoic corals, there await disappointment, discouragement and 
not infrequently entire disgust. Well equipped with specimens 
though he may be, he is of necessity dependent upon the literature 
for description and classification. What with incompleteness, in- 
accuracies, contradictions and synonymy this literature often proves 
more puzzling than the fossils themselves, and may lead to its 
abandonment for more inviting fields of labor. We will suppose 
that our student has mastered, as he imagines, the generic charac- 
teristics of Amplexus, Zaphrentis and Cyatliophyllum, and finds in 
his hands for study specimens of our well known Streptelasma 
corniculum. He examines them externally, appreciates the appro- 
priateness of the specific name, notices the heavy epitheca, the 
pinnate arrangement of the costse and the characters of the calyx. 
He next makes cross and longitudinal sections and observes the 
character of the tabulae*, the absence of dissepiments and the pe- 
culiar central core. He desires now to know just how the genus 
is to be distinguished from all others, and naturally hunts up the 
original description. A form like Cyaihophyllv/m but distinguished 
by the spiral twisting together of the septa at the center. In an 
evil moment, however, for his peace of mind, he learns that there 
is not entire agreement among palaeontologists in regard to the 
20 
