144 



COELENTERATA. 



Sub-fam. 1. Porpalidae. Umbrella highly vaulted. Pneumatocyst 

 campanulate, with a radially lobate margin. PorpaUa H. (Fig. 117) ; 

 Porpema H. 



Sub-fam. 2. Porpitellidae. Umbrella flat, slightly vaulted. Pneu- 

 matocyst discoidal, without prominent radial marginal lobes. Porpitella 

 H. ; Porpita Lamarck. 



Fam. 3. Velellidae. With an elliptical, often nearly quadrangular, umbrella 

 including a polythalamous pneumatocyst of the same form, composed of numerous 

 concentric rings, and usually bearing in its diagonal a vertical crest. Marginal 

 tentacles simple, without cnidospheres ; gonostyles with mouths. A chitinous 

 prolongation of the pneumatocyst -lining into the crest is generally present. 

 The 8-radiate character of the canal system exists but is much hidden and 

 has become in part bilateral. The pneumatocyst consists of a central chamber 

 sometimes markedly 8-radiate and of many concentric elliptical rings, with 

 stigmata and pneumothyrae. Eataria Esch., pneumatocyst without crest. 

 Vclclla Lamarck ; Armenista H. 



Sub-order 2. Siphonanthae. 



Stem (coenosome} formed l>y the manubrium of 

 the original bilateral medusa. The buds arise in 

 the ventral line of this manubrium. Larva bilateral 

 (Siphonula). 



Section 1. CALYCOXECTAE. CALYCOPHORIDAE. 



Siphonanfhae with one or 

 more nedocalyces, without 

 pneumatocyst and palpons. 

 Cor in id ia ordinate. 



A typical member of this 

 group such as Diphyes (Fig. 

 118) consists of a long con- 

 tractile hollow stem bearing 

 at its upper end two opposed 

 nectocalyces or swimming 

 bells without manubria, but 

 with four radial canals, a 

 circular canal, and velum ; 

 and at regular intervals along 

 its course groups of indi- 

 viduals called cormidia (Figs. 

 119, 120). 



At the point where the 

 Fio.ns. Di'phyesacumi- stem joins the nectocalyx 



nata magnified about 8 



times, sb somatocyst. (Fig. 121), or between the 



FIG. 119. Three cor- 

 midia attached to the 

 stem (coenosome) of a 

 Diphyid (after Leuck- 

 art). D hydrophyl- 

 lium ; OS gonophore ; 

 P polyp (siphon), with 

 tentacle. The cormidia 

 separate from the stem 

 to form eudoxids. 



