324 COELENTERATA — SCVPHOZOA chap. 



commou jelly-fish of the American Atlantic shores, differs from 

 Chrysaora in having sixteen additional hut small tentacles 

 arranged in pairs at the sides of the statorhabs. 



Fam. 2. Cyanaeidae. — Semaeostomata with eiglit radial and 

 eiglit adradial pouclies, which give off ramifying canals to the 

 margin of the umbrella ; but these canals are not united by a 

 ring-canal. The tentacles are arranged in bundles on the margin 

 of the deeply lobed umbrella. 



The yellow Cyanaea capillata and the blue C. lamarcki are 

 commonly found on the British coasts. 



Fam. 3. Ulmaridae. — The gastric pouches are relatively 

 small, and communicate with a marginal ring-canal by branching 

 perradial and interradial canals and unbranched adradial canals. 



In Ulmaris prototypus (Fig. 143, p. 315) there are only eight 

 long adradial tentacles, and the lips of the manubrium are rela- 

 tively short. It is found in the South Atlantic. 



Aurelia is a well-known and cosmopolitan genus, which may 

 be recognised by the eight shallow lobes of the umbrella-margin 

 beset with a fringe of numerous small tentacles. 



Sub-Order II. Rhizostomata. 



In this sub-order the lips are very much exaggerated in size, 

 and are fused together by their margin in such a manner that the 

 moutli of the animal is reduced to a number of small apertures 

 situated along the lines of suture. Tentacles are absent on the 

 margin of the umljrella. This sub-order contains some of the 

 largest known jelly-fishes, and exliibits a considerable range of 

 structure. Tlie families are arranged by Maas^ in three groups. 



Group I. Akcadomyaria. — Musculature of the disc arranged 

 in feather-like arcades. Oral arms pinnate. 



Fam. Oassiopeidae. — There are no epaulettes on tlie arms. 

 Labial tentacles present. Cassio'peix. is common in the Indo-Pacific 

 seas, and extends into the Eed Sea. It includes a great many 

 species varying in size from 4 to about 12 cm. in diameter. 



Group II. Radiomyama. — Musculature arranged in radial 

 tracts. Oral arms bifid. 



Fam. Cepheidae. — The genera included in this family differ 



1 "Siborja" Exped. Mon. xi. 1903. 



