102 INVKRTKBUATK ZOOLOGY 



brachia, Hormiphora, etc.) have ovoid or pear-shaped bodies 

 bearing two tentacles arising from tentacular sacs or sheaths and 

 into which they may be retracted. The Lobata includes those 

 which have two large oral lobes and numerous minute lateral 

 tentacles. In the young, two large tentacles are present but in 

 later stages only their bases are present and these are without 

 a sheath. Venus' Girdle (Cestus) is an example of the order 

 Cestida members of which have the body much compressed in 

 the vertical plane. Representatives of the order Beroida lack 

 tentacles and the wide mouth and gullet occupy most of the 

 animal. 



Outline of Classification 



A. Phylum Coelenterata. — Diploblastic; radially symmetrical; bearing 

 tentacles and nettling cells; a single gastrovascular cavity with one opening; 

 no anus; aquatic. 



I. Class Hydrozoa. — Alternation of generations typical; medusa with 

 velum; pol>p without entodermal folds. 



1. Order Leptolinae. — Hydroid fixed. 



a. Suborder Anthomedusae. — Polyp without theca; gonads on 

 manubrium; Hydra, Clava, Cordylophora, Coryne, Tu bular ia, 

 Bougairwillia, Hydradinia. 



b. Suborder Leptomedusae. — Polyp with theca; gonads on 

 radial canals. Obelia, Go iiionemu s. Campanidaria, Sertularia, 

 Aequorea, Plumularia. 



2. Order Trachylinae. — Medusa develops directly from egg. 



a. Suborder Trachymedusae. — Tentacles on bell margin; 

 gonads on radial canals. Petasus, Trachijnema, Liriope, Cam- 

 panella, Aglantha. 



b. Suborder Narcomedusae. — Tentacles arise from aboral 

 surface of bell some distance from margin; gonads on manubrium. 

 Cunina, Aeginopsis, Cunocantha. 



3. Order Hydrocorallina. — Massive calcareous exoskeleton. Mil- 

 lepora, StTjIasUr. 



4. Order Siphonophora. — Pelagic; colonial with marked poly- 

 morphism. Phmadia, Vclella. 



II. Class Scyphozoa. — Usually alternation of generations; medusa 

 without velum; gastric tentacles; polyp with four entodermal folds. 



1. Order Stauromedusae. — Conical or vase-shaped medusa; no 

 marginal sense bodies. Tessera, Haliclystus, Lucernaria. 



2. Order Peromedusae. — Cup-shaped medusa; four interradial 

 sense bodies. Pericolpa, Pcriphylla. 



3. Order Cubomedusae. — Cuboidal; four perradial sense bodies. 

 Charyhdea. 



4. Order Discomedusae. — Saucer-shaped medusa; eight or more 

 otocysts. 



