﻿American Palcsozoic Fossils. 



29 



the zoarium have, as usual, thin walls; they are never vertical, but 

 proceed obliquely toward the surface, almost immediately after develop- 

 ment. In the mature " or peripheral region, which is larger than 

 in any other species of the genus known to me, their walls are much 

 thickened, and the successive stages of growth are marked by bands 

 of sclerenchyma parallel with the surface. The spiniform tubuli are 

 peculiar, and, under a high power, appear to consist of a large num- 

 ber of exeessivety minute dark spots, which are irregularly arranged 

 in vertical series. If I am right in my belief, then these spots repre- 

 sent the other ends of small canals, by means of which the spiniform 

 tubuli were brought into communication with the visceral cavities of 

 the zooecia. In the wall substance immediately surrounding the lat- 

 ter they are very distinct, and certainly hollow. Diaphragms very 

 few, or absent. 



Near the center of transverse sections (PI. 1, fig. 2a) the tubes are 

 small ; in the second cycle they have nearly attained their full size 

 while some of the third cycle ma} 7 be traced to their apertures at the 

 surface of the branch. In the peripheral region the tubes are cut 

 longitudinally, and present characters already noted in describing 

 this region of a vertical section. 



This species is perhaps more nearly related to B. lepidod^endroidea, 

 Meek, than to any other species of the genus. They differ, conspicu- 

 ously, however, in several respeafcs. Well-preserved examples of the 

 two species are readily distinguished from each other by their surface 

 peculiarities. The vestibules of the zooecia in Meek's species are more 

 distinct, and rhomboiclal, which is not the case in B. crassa, while the 

 cells of the latter are larger and not so regularly arranged as those 

 of the type species. The single large spiniform tubulum, which is 

 apparently always developed at the ends of the cells in B. lepidoden- 

 droidea, is wanting in B crassa. while the usual spiniform tubuli of 

 the latter are larger than those of Meek's species. Further, where 

 examples of B. lepidodendroidea are worn, the interspaces are 

 smooth, and the spiniform tubuli are not represented by small pits, as 

 is certainly the case in B. crassa. As will be seen by comparing the 

 figures of the two species given on PI. I., their sections present equally 

 important differences. 



Formation and locality: In the Upper Coal Measure deposits at 

 Kansas City, Mo., where it is associated with, but less common than 

 B. lepidodendroidea. 



