STYLASTERINA 285 



greater part of the gonad. The spermatozoa escape through a 

 peculiar spout-like duct which perforates the superficial wall of 

 the ampulla. In some genera (Bistichopora) there are several 

 male gonophores in each ampulla. 



The gonophores of the Stylasterina have been regarded as 

 much altered medusiform gonophores, and this view may possibly 

 prove to be correct. At present, however, the evidence of their 

 derivation from Medusae is not conclusive, and it is possible 

 that they may have had a totally independent origin. 



Bistichopora and some species of Stylaster are found in shallow 

 water in the tropics, but most of the genera are confined to 



Fig. 136. — A portion of a branch of Cryptohdia ramosa, showing the lids 11 and 12 

 covering the cyclosystems, the swellings produced by the ampullae in the lids amp^, 

 amp^, and the dactylozooids, dac. x 22. (After Ilickson and England. ) 



deep or very deep water, and have a wide geographical distribution. 

 No species have been found hitherto within the British area. 



A few specimens of a species of Stylaster have been found in 

 Tertiary deposits and in some raised beaches of more recent 

 origin, but the order is not represented in the older strata. 



Fam. Stylasteridae. — All the genera at present known are 

 included in this family. 



Sporadopora is the only genus that presents a super- 

 ficial general resemblance to Millepora. It forms massive, 

 branching white coralla, with the pores scattered irregularly on 

 the surface, and, like many varieties of Millepora, not arranged 

 in cyclosystems. It may, however, be distinguished at once by 

 the presence of a long, brush-like style in each of the gastropores. 

 The ampullae are large, but are usually so deep-seated in the 

 coenenchym that their presence cannot be detected from the 

 surface. It was found off the Eio de la Plata in 600 fathoms 

 of water by the " Challenger." 



