222 THE AUSTRALIAN HYDROMEDUS.E, 



IV. SUB-FAMILY. SERTULARIN^. 

 SERTULARID/E. Hincks. 

 Alimentary Zooicls, invested by chitinous cups, which are more 

 or less adnate to the stem, and never possess separate Hydrocauli. 

 Lineolaria. Hincks. 

 Sertularia. Linne. 

 Diphasia. Agassiz. 

 Sertularella. Gray. 

 Pasythea. Lamouroux. 

 Idia. Laumouroux. 

 Thuiai'ia Fleming. 

 Hydrallmania. Hincks. 

 Triplograptus. Richter. 

 Corynoides. Nicholson. 

 Dendrograptus. Hall. 

 Callograptus. Hall. 

 Dictyonema. Hall. 

 Ptilograptus. Hall. 

 Thomnograptus. Hall. 

 Buthograptus. Hall. 

 Tnocaulis. Hall. 



G. FAMILY. GRAPTHOLITHID^:. 



Possessing a chitinous Endo- and Exo-skeletori. The former 

 rod-shaped. Colonies free swimming, probably extinct. From 

 the Cambrian to the lower Devonian. 



I. GROUP. GRAPTOLIDEA. Lapworth. 

 Hydrosom developed from a Sicula, every canal containing 

 Coenosarc, bears only one row of cells. Axis (Virgula) on the 

 dorsal side in a furrow of the inner lamina. 



A. MONOPRIONID/E. 

 Hydrotheca? in oue row opposite the axis. 



