282 



Family Adeonidae Busk^ 



The zooecia, the entire frontal surface of which is provided with a frequently 

 strongly coloured covering membrane, are always without spines, extremely thick- 

 walled and strongly calcified. There are generally pores, and the partition walls 

 are provided with numerous (in the distal half of the zooecium usually 14 — 16), 

 small, uniporous rosette-plates disposed in a single row, which on account of the 

 thickness of the walls appear at the end of long canals, and the pores appear in 

 a similar way. Owing to the continued deposition of calcareous matter a second- 

 ary, sometimes even a tertiary, aperture is always present. This is more or less 

 different from the primary one, which has most often a sinus or a concave proxi- 

 mal margin. The operculum is generally well marked off from the covering mem- 

 brane. Avicularia are hardly wanting in any species and occur in most species 

 both as dependent and independent. They are always without a calcified trans- 

 verse bar between the opercular and the subopercular area, and at its base the 

 mandible has on either side a strongly protruding muscular process. Ooecia are 

 wanting, but gonozooecia appear in most species. The latter are somewhat larger 

 than the ordinary zooecia, from which they further differ by possessing a broader 

 aperture and by being generally better provided with pores. The colonies are 

 usually free, two-layered, sometimes laminate, sometimes branched, more rarely 

 incrusting. 



This extremely natural and sharply delimited family was founded by Busk 

 in his report on the Bnjozoa of the Challenger Expedition. But just as the author 

 did not succeed in comprehending this family in all its extent, overlooking as 

 he did, that his ^Mucromllai- pyriformis, set up in the same work, also belongs 

 to it, so also is his diagnosis of the family very incomplete, as of real, general, 

 positive characters he mentions only one, viz. the above-mentioned peculiarity 

 in the avicularian mandible, which however according to Waters^ may also be 

 found in members of other families. On the other hand. Waters' has pointed 

 out that the median pore which according to Busk is found in all members of 

 this family can not be regarded as a family character, as this pore in some spe- 

 cies leads into the zooecial cavity itself (Adeona, Adeonellopsis), while in others it 

 leads into the space between the primary and the secondary aperture (Adeonella). 



This incomplete diagnosis of the family may be one of the reasons for the 

 fact, that in spite of its naturalness this family has not been adopted by a single 



» 8, p. 177. ^ 106 a, p. 777. ' 106, p. 283. 



