Type locality: Arraial do Cabo, Rio de Janeiro, Brazil.

Type: MNHN-LBIM.C. 1989.2 (holotype /alcohol). Arraial do Cabo (Enseada), Rio de Janeiro, Brazil. Collected by G. Muricy (16 December 1986).

Citations: Klautau et al. (1994); Klautau & Borojevic (2001).

Colour: White in life and when preserved.

Description: Cormus massive, formed of thin, regular and tightly anastomosed tubes. Oscula are simple openings, surrounded by a thin membrane, and located on the top of short conical projections. They receive water from large water-collecting tubes.

The skeleton comprises three kinds of spicule: triactines, tetractines (Fig. 7A) and tripods (Fig. 7B). The triactines and tetractines are equiradiate and equiangular, with conical actines and blunt tips. The apical actine (Fig. 7B) of the tetractines is shorter and thinner than the facial ones, and it is conical, sharp and covered with short spines. This actine is always projected towards the inside of the tubes. Tripods are more irregular than the triactines and tetractines, and frequently they are sagittal. They normally have their centre raised but sometimes look like large conical triactines. However, it is possible to distinguish them from large triactines because of the strong conical shape of their actines and because of their location. They are distributed on the surface of the external tubes in a monolayer, delimiting the cormus. Habitat is sciaphile.

Remarks: Specimens are morphologically very similar to those of C. cerebrum from the Mediterranean Sea. However, they were recognized as a distinct species after genetic studies (Solé-Cava et al., 1991) showed that there was no gene flow between the two populations, resulting in a very low level of genetic identity. The only morphological differences found here were in the size of the spicules, which are a little longer and thinner in the Mediterranean population (triactines: 85 Mm (±7 Mm)/7 Mm (±1 Mm); tetractines: 83 Mm (±9 Mm)/7 Mm (±1 Mm); tripods: 89 Mm (±15 Mm)/11 Mm (±2 Mm)), and in the spines of the apical actine, which are also longer in C. cerebrum and very short in C. brasiliensis.