182 INVERTEBRATE ZOOLOGY 



Order 1. ASCONIDA. Calcareous sponges with thin body-wall 

 pierced by pores. Ex. Leucosolenia. 



Order 2. SYCONIDA. Calcareous sponges with moderately 

 thick body-wall in which are numerous straight radial canals. 

 Ex. Grantia. 



Order 3. LEUCONIDA. Calcareous sponges with thick body- 

 wall in which are branched radial canals. Ex. Leucetta. 



Class II. Noncalcarea. Sponges with silicious spicules, horny 

 fibers, or without skeletal structures. 



Order 1. MYXOSPONGIA. Sponges without skeleton. Ex. 

 Halisarca. 



Order 2. SILICISPONGIA. Sponges with silicious spicules. 

 Ex. Spongilla. 



OrderS. KERATOSPONGIA. Sponges with horny fibers. Ex. 

 Euspongia. 



Type II. CNIDAKIA. Gastrozoans in whose body-wall are 

 nettle cells or adhesive cells for catching prey. 



Class I. Hydrozoa. Usually minute jelly-fishes or hydroid polyps, 

 the former with a velum and the latter without mesenterial ridges. 



Order 1. A UTHYDRJE. Hydrozoans in which the adult animal 

 is a simple hydroid polyp, no medusoid generation being present. 

 Ex. Hydra. 



Order 2. HYDROMEDUSJE. Hydrozoans with alternation of 

 generations ; both hydroid and medusoid generations usually present. 



Suborder 1. Tubidarice. No hydrotheca present ; medusae bell- 

 shaped with genital organs on manubrium. Ex. Pennaria. 



Suborder 2. Campanularice. Hydrotheca present ; medusas disc- 

 shaped with genital organs on subumbrella over radial canals. 

 Ex. Obelia. 



Order 3. A UTMEDUS^E. Hydrozoans in which the adult ani- 

 mal is a medusa ; no hydroid generation present. 



Suborder 1. Trachomedusce. Solitary Autmedusae. Ex. Zygo- 

 dactyla. 



Suborder 2. SiplionopJiora. Colonial Autmedusae. Ex. Physalia. 



Class II. Scyphozoa. Cnidarians in which the jelly-fishes, when 

 present, are large and opaque and without a velum ; the polyps, 

 with mesenterial ridges. 



