576 DR. R. VON LENDENFELD ON THE SYSTEMATIC [DcC. 21, 



Classis SPONGI^, auctorum. 

 Coelenterata with branching canal-system, the organs of which 

 are developed from cells of the mesogloea or primary mesoderm. 

 With simple epitheliaj with entodermal collar-cells, and without 

 movable appendages and cnidoblasts. 



I, Subclassis CALCABEA, Grant. 

 Sponges with a skeleton composed of calcareous spicules. 



I. Ordo CALCISPONGI^, BlainviUe. 

 The only order, with the characters of the subclass. 



I. Subordo Homoccela, Polejaeff, emend. 

 The entodermal epithelium consists exclusively of collar-cells. 



1. Familia AsconidjE, Hiiekel. 

 Simple sac-shaped gastral cavity with smooth surface. 

 Leucosolenia, Polejaeff, Ascetta, Ascissa, Ascilla, Ascaltis, Ascor- 

 tis, Asculmis, Ascandra, Hackel. 



2. Familia HoMODERMiDiE, Lendenfeld. 



The gastral cavity forms caecal outgrowths, which resemble the 

 tubes of Syconidse. 



Ascaltis canariensis, Hiiekel, Ascaltis lamarckii, Hackel, and 

 Homoderma sycandra, Lendenfeld. 



3. Familia Leucopsid^, Lendenfeld. 



A colony of Ascon-persons which are imbedded in the thick 

 mesogloea. There are narrow inhalant pores and wider exhalant 

 ones. The latter lead into a pseudogaster. 



Leucopsis, Lendenfeld, and some species of Pseudonardorus-forms 



II. Subordo Heteroccela, Polejaeff, emeud. 



The entodermal epithelium is differentiated into collar-cells, 

 which are found in the walls of the ciliated chambers only, and into 

 flat pavement-cells, which clothe the walls of the exhalant canals and 

 gastral cavity. 



4. Familia Syconid^, Hackel. 



With regular, radially disposed cylindrical ciliated chambers, which 

 open direct into the sac-shaped gastral cavity. 



1 . Subfamilia St/conince, Lendenfeld. 



The unbranched ciliated chambers remain isolated in their distal 

 part. 



Sycon, Polejaeff, the subgenera of Hack el's Syconidse which ter- 

 minate with the syllable ^' aga." I divide this subfamily according 

 to Hackel's scheme into the seven genera Sycetta, Sycissa, Sycilla, 

 Sycaltis, Sycortis, Syculmis, and Sycandra, 



