°^^"' THE STRUCTURE OF THE GRAPTOLITES. 241 



/J. 



fO. 



tw - 



— ms 



Structure of Retioloidea. 



Fig. 10.— Siomatogyaptus turnquisti, part of the net-work. Fig. ii. — Retiolites 

 geinitzianus, the main strands of the net-work. Fig. 12.— Retiolites nassa, proximal end 

 from the anti-virgula side. Fig. 13.— The same from the virgula side. Fig. 14.— 

 Distal end of same, showing main strands only. Fig. i^.—Dictyonema rarum, a portion 

 from the side, showing nest-shaped organs. All greatly enlarged. 



tw, thecal wall, im, thecal mouth, rt, rudimentary theca. v. virgula. rv, straight 

 virgula. zv, zigzag virgula. il, inner strand, pi, parietal strand, ml, mouth strand. 

 tns, main side strand, limiting the thecal field and the anti-virgula field, ic, initial 

 canal. 



