On the genus Coelocalypta (Porifera : Demospongiae) and other related fistulose halichondrid genera.

Coelocalypta is a fistulose halichondrid genus very close to others like Ci ocalypta and Collocalypta. The genus has been synonymyzed and the species h itherto known as Coelocalypta porrecta, C. aderma and C. hyaline were trans ferred to other genera by some authors. However, after examination of sever al specimens of Coelocalypta porrecta from the Gulf of Cadiz and type mater ial from the species Coelocalypta porrecta, Coelocalypta aderma, Ciocalypta penicillus, Ciocalypta microstrongylata and Collocalypta digitata, we prop ose the validity of these genera based on 1.- the ectosomal skeleton of the fistule: tangential in Ciocalypta, palisade-like in Coelocalypta, and abse nt in Collocalypta; 2.- the skeletal arrangement in the basal mass of the b ody: halichondroid-confused in Ciocalypta/Coelocalypta and plumose in Collo calypta; 3.- the presence of a tangential ectosomal skeleton in the basal m ass in Ciocalypta, absent in Coelocalypta/Collocalypta. In this way, the ge nus Coelocalypta would include the species Coelocalypta porrecta which is h ere redescribed on the basis of SEM observation of new material, as well as Coelocalypta microstrongylata n. comb. Moreover, the new genus Pseudohymen iacidon is proposed to include the species Coelocalypta aderma.