10 Enoin Hinckley Barbour 



specimens. This is a task of no small moment, but it will 

 eventually be done. 



It is an interesting fact in this connection that these small 

 tubules seem to grow more densely clustered as we pass in- 

 ward, and finally, as it were, thicken into a white, solid, 

 compact wall. Sometimes this wall is nearly an inch thick, 

 and a pretty fair idea of it can be obtained from Plate III, Fig. 2. 

 Within this wall, and circumscribed by it, is a core of 

 sand-rock irregularly traversed longitudinally by large tubes, 

 and transversely by minute tubules. 



A section cut across this compact, hard, nearly homogeneous 

 wall, when examined under the microscope, shows plant tissue 

 arranged in fibres, apparently exactly like those on the outside; 

 and the whole looks as if the adjacent tubules bad so thickened 

 their walls that they had come in contact and formed one hard 

 solid white mass. When the superficial net-work of interlacing 

 tubes is broken away from the fossil it leaves below a rock of 

 shell-like whiteness. 



In case of exposure, this delicate tube structure, so nicely 

 brought out thereby in some cases, is sometimes almost entirely 

 weathered away in others, but a cross-section of the specimen 

 will plainly show its presence, in the latter as well as the 

 former. 



Another point which seems to be established is, that the 

 tubules so numerous on the surface extend in limited numbers 

 in every direction entirely throughout the specimen from the 

 side walls to the center of the corkscrew. 



The tubules which traverse this central core, are continua- 

 tions of those on the surface, and differ in no respect now 

 apparent. This perhaps may rank as evidence of a certain 

 kind, that these fossil spirals had a purely vegetable origin. 

 Unless perchance we conceive of an imaginary plant as having 

 lined this old time burrow, or assume that the plant structure 

 observed is simply that of the plant-food with which the old- 

 time gopher lined his hole. 



10 



