EETECAYA. 
187 
RETEC A V A, d’Orbig-ny, 1854. 
Synonyms. 
Itetecava, d’Orbigny (1854), Hamm (1881), etc. 
Retepora, pars, Groldluss (1827), M. Edwards (1836). 
Idmonea, pars, you Hagenow (1851), 
Reticulipora, pars, d’Orbigny (1850). 
Reteporidea, d’Orbigny (1849), d’Orbigny (1850). 
Crisina, pars, d’Orbigny (1854). 
Crisidmonea, Marsson (1887). 
Diagnosis. 
Crisina in whicli the zoarmm is erect and formed of laterally 
compressed branches. The branches divide dichotomonsly or 
irregularly, or are pinnate. The sub-branches may remain 
free or may unite into a reticular network. 
Apertures in the transverse series are numerous and regular. 
Xo unpaired median series. The reverse side is occupied by 
an axial rod formed of rudimentary zooecia and the distal 
ends of zooecia (‘ canaux de renforcement ’ of Pergens). 
Type SpEcrES. 
Retepora clathrata, Goldfuss, 1827. Maastrichtian : Maastricht. 
Affinities. 
This genus was founded by d’Orbigny for a single species 
described by Groldfuss as a Retepora. From d’Orbigny’ s account 
it is clear that he considered its main character to be the existence 
of the “ cote germinate longitudinale ” ; but for reasons stated on 
p. 129 the value of this character is doubtful, and the genus is 
here accepted on account of the axial rod or thickening on the 
reverse edge. This structure occurs also in Marsson’ s Crisidmonea, 
and it seems to offer the best chance of the generic separation of 
the Retecava- Crisidmonea series from Crisina. Marsson, however, 
attached more value to the successive calcareous laminae which 
occur on the surface of the zoarium, as the main feature of 
Crisidmonea. That these layers are equally well developed in 
Retecava clathrata is shown by a section figured on p. 189. 
The genus Reteporidea has also to be included as in part a 
synonym of Retecava-, for it was founded by d’Orbigny ^ in 1849 
^ D’Orbigny. Gen. nouv. Bry. ; Eev. Mag, Zool. ser. 2, vol. i. p. 500. 
