100 CARBONIFEROUS PERIOD. 



space of two millimeters, measured parallel with the axis of the stem, and 

 seven or eight in the same space measm-ed along one of the oblique rows. 

 The variation of the latter measurements in different specimens is not 

 proportionally so great as the variation of the diameter of stems, because 

 the angle of the oblique rows with the axis is greater in large stems than 

 in small ones; this gives the cell-apertures a greater proportional width in 

 large stems, while the actual width is nearly uniform in all. 



Most of the examples in the collection are considerably larger than 

 the type-specimens of Mr. Meek, but some of them agree perfectly with 

 his types as to size, and the structure is identical in all, so far as can be 

 detennined. Specimens, apparently of this species, from the Upper Coal- 

 Measures of Northern Missouri and Southern Iowa, are still larger than 

 any contained in the collections. Some of the specimens of the collections 

 are more or less completely silicified, and one or two of them have a hollow 

 axis. This seems to have resulted from the failui'e of the central portion 

 to become silicified like the outer portion, which, remaining calcareous, was 

 subsequently removed by dissolving agencies that the outer silicified por- 

 tion resisted. Tlais is really shown to be the case by the breaking of others, 

 and finding the central portion yet calcareous and retaining the structure 

 of the coral, the parts of which structure being in dhect continuity 

 with those of the outer silicified portion. On the other hand, a fragment 

 of a species of this genus obtained from the Subcarboniferous limestone of 

 "Washington County, Indiana, seems to have a hollow axis, the whole of 

 the coral being calcareous. It is, however, not certain that the axis of even 

 this example was originally hollow. 



Position and locality. — Strata of the Carboniferous period ; west face of 

 Oquirrh range, near "E. T. City", Utah, and at the confluence of White 

 Mountain and Black Rivers, Aiizona. 



Genus SYRINGOPORA Goldfuss, 1826. 

 Syringopora multattenuata McChesney (?). 



From strata of the Carboniferous period, at various locahties in 

 Nevada and Utah, specimens of a species of Syringopora _ Avere obtained. 

 They are too imperfectly preserved for satisfactory specific identification, 



