XII. CRUSTACEA AND LOWER INVERTEBRATA. 99 



The first two classes of this division are represented in the 

 collection, the Scyphomedusce or Jelly-fishes by Phyllorldza 

 punctata (type specimen) ; and the Siplionojohora by Physalia 

 megalista (the Portuguese man-of-war), and by specimens of 

 For pita, Velella, and Diphyes^ the only Australian genera. (See 

 Case 17.) 



Class III. — The HYDROMEDUS^. — This class is 

 largely represented in the collection. It is divided into three 

 orders : — 



1. — HydrOCOralliae. — Coral-like polyps with stocks having a 

 calcareous skeleton, tubular hydrothecse, and two kinds of 

 polyps, some possessing a stomatic cavity, which in others 

 is wanting. Millej^ora alcicornis, Stylaster gracilis^ and 

 Distichopora violacea are well known species. (See 

 Case 10.) 



2.— Tubulariae.— Polyps without hydrothec^, the stems 

 only in some cases having a chitinous envelope. Tuhularia 

 gracilis and Pennaria australis are examples. (See 

 Case 17.) 



3. — Campanulariae.— The members of this order usually 

 present many branched plant-like tufts, possessing cup- 

 shaped hydrothecae, into which, in most cases, the polyp 

 heads can retire at will. The following are the chief 

 families into which it is divided : — 



Family I. Plumidariidce. — In the animals composing this 

 family the hydrothecae are arranged in single rows, usually on 

 the upper surfaces of the branches, and have small accessory cups 

 containing stinging cells or nematocysts. Plumidaria rubra 

 Aglaophenia divaricafa, and Halicornaria ascidioides, all from 

 Port Jackson, are representatives of the family. (See Case 17.) 



Family II. Sertulariidce. — Often much branched, with 

 flask-shaped hydrothecae arranged in opposite or alternating rows 

 on each side of the stems and branches. Sertidaria elongata, 

 Diphasia pinnata, Sertidarella divaricata, Pasythea quadridentata, 

 Iclia pristis, and Thuiara lata are good examples of the family. 

 See Case 17.) 



