214 ROCHESTER ACADEMY OF SCIENCE. 



the same spiral. These plates have essentially the same structure seen 

 in Taomcrus, — a series of curved lamellae, lunate in section, and a 

 marginal cylinder. They also penetrate one another and themselves, 

 and like it were formed downward. A comparison of the two genera 

 makes unavoidable the conclusion that they originated in the same 

 way, that is, that Taonuriis like Dcedalus was formed by successive 

 packings of sediment along the radial side of a curved burrow which 

 was shifted with each packing, the aperture as a rule remaining 

 stationary. The packings are represented by the lamellae, the burrow 

 by the marginal cylinder. The distal end of the cylinder w^as formed 

 by successive fillings in the blind end of the burrow, the ascending 

 portion, by the filling finally of the burrow itself. The burrow- 

 extended nearly horizontally in the sediment instead of nearly 

 vertically, as in Dcedahis. When the packing was principally in the 

 lower portion, an elongated plate, U-shaped in outline was formed, the 

 burrow gradually lengthening with each shifting. When the material 

 was distributed along the side of the burrow for the greater part of its 

 length, the displacement became lateral as well as longitudinal and 

 resulted in the formation of a spiral plate of increasing dimensions, the 

 burrow rounding in at the base being the generatrix of the volutions 

 and axis of the structure. \'ariations in the way in which the sedi- 

 ment was disposed of produced corresponding variations in outline. 

 Sometimes in the spirals the deviations in direction led to the burrow's 

 passing through some portion of its former path, producing the self- 

 penetrations described. 



It seems likely, as in Dcedahis, that the animal which produced 

 these structures was a sedentary polychaetous annelid. 



Dictyodora liebeaua Weiss, which has been compared to, Taomi- 

 rus {Spirop/iytoji) and Daedalus, is probably of the same nature as 

 these. 



The forms included under Taomirus by Saporta and others, and 

 now recognized as belonging to the genus RhizocoraUium Zenker 

 {Glossifungites Lomnicki), were produced by the packing of sediment 

 along the radial side of a reclining U-shaped burrow of two openings, 

 as it was repeatedly shifted and lengthened. The species described as 

 Arenicolites duplex Williams was produced in the same way, instead 

 of by the filling of grooves in the surface of the mud. 



