Genus Halisarca Johnston, 1842

Diagnosis. Chondrillida in which the choanocyte chambers are tubular, branched and wide mouthed. Larvae are incubated disphaerulae (a larval form found only in Halisarca) with simple undifferentiated histology and cilia of uniform length. Skeleton is composed of fibrillar collagen only, there are no fibrous or mineral elements present; ectosomal and subectosomal collagen is highly organised and structurally diversified (Ereskovsky et al. 2011).