214 Christmas Island. 



done so on the character of the columella. But in the type 

 species of Cceloria the columella is quite well developed (see e.g. 

 the orig:inal figure of Ellis & Solander, Hist. Zooph., pi. xlvi, 

 figs. 1, 2); it is in fact better developed than in some species 

 of Mccandrina. 



The distinction based on the columella appears to me insufiicient 

 for the separation of the two genera. The length of the confluent 

 calicinal series may, however, pclcl an adequate basis ; for those 

 corals in which the calicinal series are verj" long may be con- 

 venicntl}' kept distinct from those in which the calicinal series- 

 arc short and independent calices predominate. Cceloria, with 

 C. dccdalea as the type, would include the latter group. The naming^ 

 of the former group is a difficult question. The most convenient 

 name would be Mmandrina, but that name would have to be 

 designated as Ed. & H., 1848, non Lamarck, 1801. Eor according 

 to the original foundation of that genus its type is Mceandrina 

 pectinata, Lam., which most authors have taken as the type of the 

 genus Pcctinia. 



AVhether the inconvenience of the change in the name 

 Mmandrina, which observance of the laws of nomenclature would 

 involve, be too serious for obedience to the law to -be advisable^ 

 I leave zoologists to settle, and so provisionally retain it. 



Goniastrsea retiformis (Lamarck), 1816. 



Astrcea retiformis, Lamaixk, 1816. Hist. nat. Anim. s. Vert., vol. ii, p. 265. 

 Goniasfrcea retiformis, Edwards & Haime, 1849. Mem. Astr., pt. iii : Ann. 

 Sci. nat., Zool., ser. iii, vol. xii, p. 161. 



This species is represented at Christmas Island by a recent 

 specimen determined bj- Mr. Bernard and several fossil specimens. 

 The latter show the following characters : — The corallites are from 

 3-4 mm. in dia. ; the walls are from '5 mm. to something under 

 1 mm. in thickness ; the septa belong to three cycles, of which the 

 third is incomplete ; the columella is loose and sometimes hollow ; 

 the pali arc indistinct ; the corallites are elliptical, quadi'angular, 

 pentagonal, or hexagonal in shape. 



The corals agree closely with G. capitata, Stud.,' which, as 

 Ortmann^^ suggests, is probably a variety of G. retiformis with 

 thinner walls, somewhat exsert septa, and more open calices. The 

 recent specimen from Christmas Island resembles the capitata fonn, 

 the characters of which are not preserved in any of the fossils. 



Distribution. — Christmas Island. 

 Eecent : 



Fringing Eeef, Elying Fish Cove. 



' Th. Stiider, Beitr. Fauna Steinkor. Singapore : Mitth. Naturf. Gesell. 

 Bern., 1880 (1881), pp. 40, 41, fig. 8. 

 ^ Ortmann: op. cit., p. 173. 



