(Fig. 2)

Etymology: Named after the late Mr Vernon Crookes who donated the property that is now the Vernon Crookes Nature Reserve, in which this and other earthworm species are protected.

Material examined: SOUTH AFRICA: KwaZulu-Natal: Holotype: NMSA / Olig. 00770 clitellate, Vernon Crookes Nature Reserve (30º18'S: 30º40'E), 6 km N. of Tourist Camp, primary grassland, 22 November 1989. Paratypes: NMSA / Olig. 02554 1 clitellate, abscised, collected together with holotype; NMSA / Olig. 00844 1 clitellate, 3 km from type locality, on bank of small water pool, 23 November 1989; NMSA / Olig. 00828 2 clitellate, 1 km W. of type locality, dug out from black soil at ca. 45 cm depth. Other material: NMSA/00748 1 clitellate, 8 March 1989; NMSA / Olig. 00766 2 abscised anterior parts, 23 November 1989; NMSA/00768 7 specimens manifesting clitellum by brown colour, 7 March 1989; NMSA / Olig. 00769 1 specimen with abnormally regenerated body part in area of clitellum, 23 November 1989. All paratypes and other material collected in neighbourhood of type locality by J. D. Plisko.

Description based on holotype and paratypes.

External characters:

General: Body cylindrical. Colour: In life dorsally violet, ventrally yellowish-grey; alcohol-preserved brownish-grey, with violet tint. Dimensions: Holotype somewhat contracted 170 mm long, 6 mm wide at 10, 8 mm at tubercula pubertatis; clitellate paratype 120 mm long, 6 mm wide at 10, 7 mm wide at tubercula pubertatis; juvenile paratypes 125–135 mm long, 5 mm wide. Segment number: Holotype 249; clitellate paratypes 169–328, regenerating individual 112, abscised 84+. Prostomium: Prolobous, small. Segmentation: Secondary annulation present on preclitellar segments; 1 and 2 short, not clearly separated, both with irregular longitudinal grooves; 3 simple, 4–8 with 2 simple ringlets similar in size and appearance; 9 with 2 irregularly annulated ringlets, second shorter than first; 10 and the following simple. Setae: Moderate in size; on preclitellar segments ab paired distantly, postclitellarly closely paired with ab = cd, aa > bc; first pairs of ab on segment 3. Nephridial pores: First pair in intersegmental furrow 3/4. Female pores: In 14, medially. Male pores: In area of tubercula pubertatis, in intersegmental furrow 14/15, with small swollen lips. Spermathecal pores: Only in intersegmental furrow 12/13, dorso-laterally in clitellar area.

Clitellar region (Fig. 2): Clitellum: Well developed on holotype and paratypes on 12–22, segmented; clearly bordered anteriorly and posteriorly. Ventral borders on 12– 1/n18 parallel with dorsal edges of tubercula pubertatis; on 1/n18–22 extends to ventral lines of tubercula pubertatis. Tubercula pubertatis: Irregular oval, on segments 1/n14– 1/n18, embracing the swellings of male pores; anteriorly narrower, with ventral borders much above b setal lines, posteriorly extending scarcely more latero-medially. Papillae: Small swellings associated with ab setae on 10–12 and 19–22, 23; paired or single.

Internal characters:

Septa: Septa 4/5 very much thickened, muscular, 5/6 6/7 very thin; 7/8 8/9 thickened moderately, both similar in size and appearance; other septa thin, firm. Gizzard: Barrelshaped, in 7; anteriorly muscular, posteriorly soft. Calciferous glands: Dorso-lateral in 9 extending into 10; separated ventrally and dorsally; connected with oesophagus in area of septa 9/10. Intestine: Commences in 12. Typhlosole: Commences abruptly as thick U-shaped tube in 19 or 20; terminates in holotype in segment 144; in complete paratype in 146; in abscised individual extends through all regenerated segments to the last segment 112. Dorsal blood vessel: Double in 5–9; in 5–7 thin adjacent tubes, in 8 moderately enlarged, separated; in 9 cordiform. Single, thin when crossing septa, and single although thicker in 10, and in the following segments. Paired dorsoventral vessels: In 4–7 simple, thin vessels, in 8 slightly enlarged, 9–11 gradually enlarging, moniliform. Nephridia: Meganephridia; coiled loops with oblong caeca.

Reproductive organs: Spermiductal funnels: Proandric arrangement (in segment 10); one pair of large funnels enclosed in sacs closely connected one with another and with seminal sacs. Vasa deferentia: In holotype not seen, covered by thick tissue of body wall. In paratype observed as single ducts running to anterior part of segment 15, and entering body wall at 14/15, where externally are noticeable male pores. Seminal vesicles: Moderate in size, anteriorly connected with spermiductal funnels at septum 10/11, extending into segment 11. Spermathecae: In only one row, close to septa 12/13; tubular, bent, two at each side; modest quantity of sperm observed in some of spermathecae. Ovaries: Large rosette-like funnels, posteriorly in segment 13, close to median line. Genital glands: Not observed.

Biological notes: Found in the soil of primary grassland conserved in the Vernon Crookes Nature Reserve. The reserve is situated in the southern part of coastal KwaZulu-Natal, surrounded by sugar cane fields and Eucalyptus plantations. This small reserve, comprising patches of indigenous coastal forest, bush clumps and extensive stands of grassland, is a valuable oasis of relict habitats. Close to the type locality of P. crookesi, four other indigenous microchaetids in two other genera were previously collected and described: Tritogenia curta Plisko & Zicsi, 1991, Microchaetus vernoni Plisko, 1992, Microchaetus zaloumisi Plisko, 1992, and Microchaetus ambitus Plisko, 1998.

Discussion: Closely related to P. warreni (Michaelsen, 1913 a). Both species have only one row of spermathecal pores in intersegmental furrow 12/13, and thickened septa 4/ 5 7/8 8/9. However, the thickness of septum 4/ 5 in this new species distinguishes it from other species assigned to the P. warreni species-group. The position and shape of the clitellum and tubercula pubertatis also differ.