12 Trans. Acad, Sci. of St. Louis. 



although they are too imperfectly preserved for specific iden- 

 tification or description. The largest one has a diameter of 

 8 ram. 



ECHINODERMATA. 



The impressions of numerous detached joints of crinoid 

 stems are scattered throughout the sandstone, but in no 

 instance has any portion of a calyx been observed. 



VERMES. 



ScALARiTUBA MISS0URTEN8IS n. gen. and sp. 



PI. VI. f.l. 



The Vermicular Sandstone is named from the innumerable 

 worm burrows which penetrate it in every direction, there 

 rarely being a distance of more than two or three centimeters 

 between burrows in SLuy direction upon any broken surface of 

 the rock. These burrows are 2-4 mm. in diameter, subcylin- 

 drical in form, never straight for more than a few centimeters, 

 curving in all directions, and marked by transverse ridges 

 situated at distances of one or two millimeters. These 

 ridges were evidently formed by the worm as it forced itself 

 forward through the mud of the sea-bottom, the posterior 

 extremity of the animal pushing up a small ridge of the plastic 

 material behind to serve as a brace while the anterior ex- 

 tremity was forced forward. If this was the method of 

 formation of these ridges, then the direction of progress of 

 the worm itself was always away from the concave side of the 

 ridges. The burrows are now filled with material similar to 

 that which surrounds them, but it is softer and of finer tex- 

 ture so that on weathered surfaces the burrows become very 

 conspicuous by reason of the removal of this softer material. 

 Upon freshly broken surfaces of the rock, however, the bur- 

 rows are not conspicuous, but they may be detected by their 

 slightly different color, and by their softness. 



These burrows seem to be different from any of the pre- 

 viously described worm burrows, and as they are such a 

 conspicuous feature of this formation, it seems that they 

 are entitled to a distinctive name, and they are therefore 

 designated Scalarituba missouriensis. 



