134 IDMONEA. 



zoarium, and the apertures are arranged in regular transverse 

 rows. It differs by the first character from the Entalophoridse, and 

 by the second and by the branched zoarium from the Tubuliporidae. 



IDMONEA, Lamouroux, 1821. 



[Expos. Meth. p. 80.] 



Diagnosis. Zoarium adnate, or erect. Branches ridged or 

 triangular in section. Zooecia in regular transverse and usually 

 alternate series. The zoarium divides into branches, and the 

 branches usually radiate from a centre. The branches sometimes 

 anastomose. 



Type species. Idmonea triquetra, Lamx., 1821. 



Affinities. The genus Idmonea was founded by Lamouroux for 

 a species found in the Calcaire a polypiers at Ranville, which is 

 always an encrusting form. Later authors, however, not only 

 include the erect branching forms in Idmonea, but frequently 

 exclude the type species from the genus. Thus, Busk ("Crag 

 Bryozoa," p. 94) uses the erect mode of growth as one of the 

 diagnostic characters of the family Idmoniida3, while D'Orbigny 

 founds the genus Reptotubigera on the type species of Idmonea. 

 Either the term Idmonea must be used for both the erect and 

 adnate forms, or must be kept for the latter, and the former be 

 renamed. The former course seems to me to be the most con- 

 venient, as some adnate forms often curl up at the ends, and the 

 zoarium becomes semi-erect. This is therefore a case in which 

 the distinction between the erect and encrusting mode of growth 

 is not of generic, if even of specific, importance. 



Idmonea triquetra, Lamouroux, 1821. 



SYNONYMY : 



Idmonea triquetra, Lamouroux, 1821, Expos. Meth. p. 80, pi. Ixxix. figs. 13-15. 

 ,, ,, Defrance, 1821, Diet. Sci. nat. t. xxii. p. 564. 



,, Lamouroux, 1824, Encycl. Meth. Zooph. p. 462. 



Bronn, 1825, Pflanzenth. pp. 21, 43, pi. vi. fig. 12. 



,, Blainville, 1834, Man. Act. p. 420, non pi. Ixviii. fig. 2. 



,, ,, Bronn, 1837, Leth. Geogn. ed. 2, Bd. i. p. 249, pi. xvi. 



fig. 11. 



,, M. Edwards, 1838, Mem. Cris. : Ann. Sci. nat. Zool. sr. 2, 



t. ix. p. 215. 



