The genital area of Halacaridae (Acari), life stages and development of morphological characters and implication on the classification Bartsch, Ilse Zootaxa 2015 3919 2 201 259 Newell, 1949 Newell 1949 [151,548,152,178] Arachnida Halacaridae Anomalohalacarus Animalia Trombidiformes 9 210 Arthropoda genus    Typespecies.  Halacarus anomalus Trouessart, 1894.  Adults.Female GP divided; a pair of elongate or triangular plates flanking GO. Plate often with genital groove posterior to GO. Female GO elongate, with single pair of internal gac ( Bartsch 1976a: figs 22, 38, 1979b: fig. 59). Anterior pair of three pairs of pgs in striated integument or on minute median platelet, two pairs of pgs on pair of genital plates. Subgenital setae lacking. Ovipositor at rest from hardly to distinctly extending beyond GO. On everted ovipositor one pair of short basal and five pairs of elongate apical genital spines seen; the latter in a combination two anterior and three posterior pairs. Two anterior pairs of genital spines with truncate tip ( Bartsch 1976a: fig. 40). Male GP and AP contiguous, with 7–50 pairs of filiform pgs flanking genital opening and genital groove. GO shorter than in female and in more ventral position. Each genital sclerite with three (rarely two) short sgs. With single pair of small internal gac in posterior part of GO ( Bartsch 1976a: fig. 6, 1979b: fig. 58). In most females and males AE longitudinally divided into right and left half, each half with an epimeral pore.  Juveniles.With a larval and a single nymphal stage. In protonymph genital and anal plate contiguous; GP with pair of small internal gac and pair of pgs but no sgs ( Bartsch 1976a: figs 13, 31, 1979b: fig. 64). Genital area often with genital groove. Protonymph and larva with epimeral pores.   Remarks.Nineteen species are described ( Bartsch 2009a), all are psammobionts. The majority of species is recorded from the northern Atlantic Ocean; species from the Indian and Pacific Ocean differ in several characters from the boreal Atlantic species.