472 THE AUSTRALIAN HYDROMEDUS.E, 



8. SUB-FAMILY. GLADIOGRAPTIN^. 

 GLADIOGRAPTID.E. Lapworth. 

 Both axes separate. Perfect exoskeleton of chitinous fibres. 



20. GENUS. RETIOLITES. Barrande. 



Hydrosome, simple tapering towards both ends. Axes straight 

 or zig-zag shaped, often rudimentary. Cells rectangular. Both 

 rows alternating. Inner Periderm layer a wide-meshed net. 



105. RETIOLITES AUSTRALIS. McCoy. 

 This species occurs to the north-west of Keilor in Victoria (1.) 



7. FAMILY. PLUMULARIDJE. Hincks, 1868. 



Hydropolypime forming colonies, consisting of generative 

 Zooids, Polypostyls, alimentary Polyps and Machopolyps. 



All these different kinds of Polyps are invested by chitinous 

 cups, and appear regularly disposed along a stem, which in many 

 cases is regularly branched, pinnate. 



21. GENUS. PLUMULARIA. McCrady. 



From a creeping and anastomosing Hydrorhiza plumous shoots 

 arise, which bear Zooids. All the Zooids are invested by chitinous 

 cups or cupsules. The Hydrotheca? cup-shaped ; the Nematophores 

 distributed along the stem and branches. Polypostyles different 

 in the two sexes. 



The structure of several species of this genus was investigated 

 by Hamann (2), Jickeli (3), Weismann (4), and myself (5.) 



(1.) McCoy. (I.e.), Decade II., p 36, pi. XX. 



(2.) 0. Hamann. Der Organismus der Hydroiclpolypen Janaische Zeit- 

 schrift. Band XV., Seite 529. 



(3.) C. Jickeli. Der Bau der Hydroidpolypen, II. Morphologisches 

 Jahrbuch. Hand VIII., Seite 636, ff. 



(4.) A. Weismann. Ueber die Entstehung der Sexualzellen bei den 

 Hydromedusen, Seite 172, ff. 



(5.) i?. v. Lendenfeld. Ueber Wehrthiere and Nesselzellen. Zeitschr. f. 

 wiss. Zool. Band XXXVIII. , Seite 354, translated into English Annales 

 and Magazine of Natural History, 5th series. Nr. 71. 



