BROWN, RUGOSE CORALS 
67 
development, the interior views of several individuals ranging from rela¬ 
tively small to large size have been studied. 
Stereolasma rectum Hall. 
1843 Strombodes ? rectus Hall, Geol. Report 4th. District of New York, p. 209, 
fig. 5. 
1851 Cyathophyllum rectumdEvw. & H. Polyp. Foss, des Terr. Pal. 
1876 Streptelasma recta Hall, Illustrations of Devonian Fossils, pi. XIX, figs. 
1-13. 
1900 Stereolasma rectum Simpson, Bull. 39, N. Y. State Mus. pp. 205-206. 
Hall describes the species thus ( loc . cit.): 
General form turbinate, elongated, gradually expanding from the base; straight; 
surface marked by longitudinal lines, which indicate the internal laminae. 
This is an abundant fossil, sometimes appearing in pairs, but never joined 
together. It usually tapers gradually to a very small point at the base. The 
cup is very deep and the margins thin being usually flattened. 
In 1900, Simpson used this species as the type of his genus Stereolasma 
which he describes thus: 
Corallum varying in size, straight or curved, simple; calyx circular: septal 
fovea conspicuous; septa alternating in size, the larger ones continuing to the 
center, straight or very slightly twisted; between the septa at the center of the 
corallum a deposit of stereoplasma, which has the appearance of a columella; tab¬ 
ulae and dissepiments frequent. The pseudocolumella distinguishes this genus 
from Zaphrentis. \ 
It may be added that the presence of this pseudocolumella also distinguishes 
Stereolasma from Enterolasma and is the characteristic feature of the Stereo¬ 
lasma stage of the Streptelasma development. 
This species is very abundant in the Hamilton shales of the upper De- 
vonic, and perfectly preserved specimens can easily be obtained. It is a 
particularly interesting species for these studies because it is one of the species 
reported by Duerden to have six primary septa in the youngest stage and to 
develop the four-fold structure later. 1 
The collections in the paleontological laboratory of Columbia University 
are particularly rich in this species, and from some two or three hundred 
corallites I selected the most perfect individuals for this investigation. 
Some of these were found with perfect tips and some with the ends slightly 
fractured. Following the method described in the first chapter of this 
1 Annals and Magazine of Natural History, series 7, vol. XVIII, p. 236, Sept., 1906. The 
Morphology of the Madreporaria. The Primary Septa of the Rugosa. 
