20 



PALAEONTOLOGY 



would require examination of the soft parts ; and the family 

 has long been extinct. Indications of the flexible consistency 

 of the polypary, and M. Barrande's statement of the existence 

 of a cylindrical canal in its axis, which he conjectures to have 

 contained the common connecting tissue of the polypes, have 

 weighed with the writer in placing the Graptolites provision- 

 ally in the present class of Tolypi. The axis of the polypary is 

 sometimes straight (fig. 3, 3), sometimes spiral (fig. 3, 6). The 

 ordinary form, as given by the Graptolites •prioclon (fig. 3, 3), 



Fig. 3. 



Hydrozoa; Antlwzoa; Bryozoa. 



1. Protovirgularia dichotoma, M'C. ; Silurian, Dumfries. 



2. Oldhamia antiqua, Forbes ; Cambrian, Wicklow. 



3. Graptolites priodon, Bran. ; Silurian, Britain. 



4. Didymograpsus Murchisoni, Beck ; L. Silurian, Wales. 



5. Diplograpsus folium, His. ; L. Silurian, Britain. 



6. Bastritcs percgrinus, Barr ; Silurian, Bohemia. 



7. Ccenites junipcrinus, Fichw. ; U. Silurian, Dudley. 



8. Ptilodictya lanceolata, Lonsd. ; U. Silurian, Torlworth. 



9. Arcliimcdipora Archimedea, Lesuer. ; Carboniferous, Kentucky. 



10. Ptilopora pluma, M'C.; Carboniferous, Ireland. 



11. Fenestrella membranacea, Ph.; Carboniferous, Britain. 



is serrated on one side only, and is found abundantly in the 

 Cambrian or older Silurian beds of Scotland and Wales ; it 

 occurs also in the Ludlow rocks. The double ( Iraptolites 



