On the El-rant Annelides of the Older Paheozoic Rocks. 167 



of Chondrites, Falceophycus, &.C.), the author groups together imder 

 the name of Planolites. 



The second great group of Annelide-remains comprises genuine 

 surface-trails or " tracks," which of necessity never pass below the 

 surface of the bed on which they occur. Some of these remains, 

 such as Crossojiodia, are, beyond doubt, due to the operation of 

 marine Annelides ; but it may be a matter of question whether we 

 have in these cases the actually petrified body of the worm, or 

 merely the track produced by the passage of the animal over the 

 surface of the mud or sand. The author, however, gives reasons 

 for beKe^-ing that the latter explanation is truly the correct one. 

 Other fossils belonging to this group (such as Myrianites) are 

 equally, beyond doubt, produced by the operations of marine 

 animals ; but it remains quite uncertain whether they have been 

 formed by Annelides, Crustaceans, or MoUusks. Lastly, there are 

 remains which appear to be really casts of the surface-trails of 

 Annelides or other marine creatures, and which, therefore, are 

 elevated above the surface of the bed on which they occur. Such 

 remains may readily be confounded ^^uth those belonging to the 

 genus Planolites, from which they are only distinguishable by the 

 fact that they are strictly confined to a single surface of deposi- 

 tion. To fossils of this nature the author proposes to restrict 

 the generic title of Nemertites. 



Finally, the author describes some singular tracks apparently 

 produced by Crustaceans belonging to the genus Ceratiocaris, and 

 for which he proposes the generic name of Caridolites. 



The following list comprises the species of fossils described in 

 this communication : — 



A. BUEEOWS. 



I. Grenus Aee>t:colites, Salter. 



1. Arenicolites sparsus, Salter. 



2. did\Tnus, Salter. 



3. robustus, Xicholson. 



II. Genus Scolithus, Haldeman. 



4. Scolithus canadensis, Billings. 



5. linearis. Hall. 



6. verticalis, Hall. 



III. Genus Histiodebma, Kinahan. 



7. Histioderma hibernicum, Kinahan. 



IV. Genus Planolites, Nicholson. 



8. Planolites vulgaris, Nicholson. 



9. granosus, Xicholson. 



10. articulatus, Nicholson. 



B. Teails. 

 V. Genus Ceossopodia, M'Coy. 



11. Crossopodia scotica, M'Cot/. 



12. lata, M'Coy. 



