The mucilaginous, marine red alga, Scinaia hatei Børgesen (Nemaliales), collected from various coastal areas of Karachi at the northern Arabian Sea, was investigated for its morphology, anatomy, growth and reproductive structures. This represents the first detailed study of this species. Scinaia hatei was compared with three other species, S. moniliformis subsp. pakistanensis Afaq-Husain et Shameel, S. saifullahii Afaq- Husain et Shameel and S. shameelii Afaq-Husain.