52 
ANNALS NEW YORK ACADEMY OF SCIENCES 
Pseudocolumella -— the pillar-like structure in the center of the corallite 
formed by the inner margins of the primary and secondary septa 
either uniting or partly uniting near the center of the calyx. 
II. Ordovicic and Siluric Corals. 
In the limestones of the middle Ordovicic the earliest representatives 
of the rugose corals are found in North America. No individuals of this 
group have yet been found in the Cambric deposits, and those found in the 
middle Ordovicic are quite primitive and simple in their organization and 
development. They are taken as the earliest representative forms obtainable. 
Streptelasma profundum (Owen). 
1844 Cyathophyllum profundum Owen, Geological Explorations of Iowa, Wis¬ 
consin, and Illinois pi. XVI, fig. 5. 
1847 Streptelasma profunda Hall, Palaeontology of New York, vol. I, p. 49, pi. 
XII, figs. 4a-d. 
1863 Petraia profunda Billings, Geology of Canada, p. 938. 
1891 Streptelasma profundum Winchell and Schuchert, Minnesota Geological 
and Natural History Survey, Final Report, vol. Ill, part I, p. 88, pi. G, 
figs. 17-19. 
This species is the earliest representative of the genus Streptelasma in 
this country. It is found quite abundantly in the Chazy (Birdseye), Black 
River and Trenton limestones in the central and eastern parts of New York 
and in Canada. This is a small species, and in his publication cited above 
Hall describes it thus: 
Obliquely turbinate, often slightly curved near the base, expanding above 
more or less abruptly; cell profoundly deep, extending nearly to the base of the 
coral; margin of the cup reflexed; surface scarcely marked by transverse rugae; 
lamellae from 36 to 60, strong, nearly equal on the margin, but distinctly alternating 
in length within; no transverse dissepiments or celluliferous structure. 
Although this species is frequently referred to in geological and paleonto¬ 
logical literature, no complete and exhaustive study of its structure and 
development has ever been made. This is undoubtedly the most primitive 
representative of the genus Streptelasma. It is not only the earliest in its 
geological distribution but also the simplest in its structure and development. 
In 1906, Gordon called attention to the primitive character of Strepte¬ 
lasma profundum in his paper entitled “Studies on Early Stages in Paleozoic 
Corals.” 1 His studies were made on a few young silicified individuals 
1 American Journal Science, Feb., 1906, pp. 123-4 and fig. 16. 
