. Bulletins of American paleontology. 44 Bulletin 333 adult form is long and cylindrical, but some remain slenderly ceratoid (Table 4). Specimens are generally relatively straight, but have slight to moderate bends as well as several constrictions and rejuvenations (PI. 6. fig. 10). A few have right-angle bends. Periodicity of growth has been observed only in the straight por- tion of one individual, where six successive constric- tions are spaced 6 to 7 mm apart (average, mm; PI. 6, fig. 11). Septal grooves and interseptal ridges, as well as growth lines, are preserved on all specimens. A
. Bulletins of American paleontology. 44 Bulletin 333 adult form is long and cylindrical, but some remain slenderly ceratoid (Table 4). Specimens are generally relatively straight, but have slight to moderate bends as well as several constrictions and rejuvenations (PI. 6. fig. 10). A few have right-angle bends. Periodicity of growth has been observed only in the straight por- tion of one individual, where six successive constric- tions are spaced 6 to 7 mm apart (average, mm; PI. 6, fig. 11). Septal grooves and interseptal ridges, as well as growth lines, are preserved on all specimens. Attachment structures are not present. Depth of the calice is estimated to be about 20 percent of the cor- allum length in small individuals, and is probably less than 10 percent in adults. Ontogeny and internal structures. —The relationship between number of septa and corallum diameter is shown in Text-figure 18. In early ontogenetic stages (PI. 5, figs. 17-20. PI. 6. fig. 5), major septa extend to or almost to the axis, where they meet. The septa with- draw from the axis, leaving an open axial region, during intermediate stages (PI. 5, figs. 14-16, 21, PI. 6, figs. 6, 7). They shorten to half the corallum radius or less in late stages (PI. 5, fig. 22, PI. 6, fig. 8; Text-fig. 19). Major septa are generally straight to slightly curved in early stages, and become wavy by late stages in many individuals. They are thin throughout ontogeny (Text- fig. 20: PI. 6. fig. 9), but in some cases are slightly dilated in early stages. Compared with other major septa, the cardinal sep- tum is the same length or longer, and almost always the same thickness, during all stages (Table 6). The cardinal fossula is about the same width as other pairs of interseptal chambers in most specimens, but is somewhat wider in intermediate and late stages of a few (Text-fig. 21). Shapes of the fossula are as described for Streptelasma subregulare (Savage, 1913b) (Table 7). Minor septa generally project a s
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