Body length 10.9-15.2 mm (mean = 12.7mm, s.d. = 1.0, n = 30); width head capsule 0.8-1.2 mm (mean = 1.0mm, s.d. = 0.1, n = 30); length of head capsule 0.9-1.3 mm (mean = 1.1 mm, s.d. = 0.1, n = 30). Body colour grey in specimens preserved in alcohol. Body form as in Fig. XX.
Mainly dark brown, anterior region of cephalic apotome yellow. Numerous small setae present on all surfaces and head capsule slightly wrinkled. Head pattern positive Postgenal cleft narrow, bell-shaped with subtriangular extension at apex; postgenal bridge as wide as hypostomium Hypostoma rounded anteriorly with strongly pigmented anterior margin and nine apical teeth; median tooth sharp, well-developed and most prominent; lateral and intermediate teeth directly adjacent to median tooth only slightly smaller and sharp, remaining teeth less well developed; 3-6 lateral serrations; 1 + 1 lines of 9-13 hypostomial setae parallel to lateral margin; 2 + 2 (rarely 3 + 3) setae in posterior half of hypostoma Antennae long and pigmented with segment ratios approximately 0.05-0.1:0.1:0.7-0.1 (n = 6) Mandible with second comb tooth longer than first and third; two mandibular serrations, posterior smaller than anterior; mandibular combs well developed. Maxillary palps heavily pigmented; three times as long as wide at base. Labral fan with 60-80 rays (n = 6).
Grey dorsally and ventrally. Cuticle without setae. Proleg with plate heavily sclerotised with a band of over 60 processes. Pupal respiratory gill histoblast dark brown, claviform.
Usually completely grey dorsally, progressively paler ventrally, especially towards posterior where last segments white; feint segmental banding visible ventrally. Ventral nerve cord grey. Ventral papillae absent. Cuticle mainly lacking setae except area around anal sclerite. Anal sclerite well sclerotised with posterior arms extending to 70-90th row of posterior circlet hooks, anterior arms bifid at apex; no sclerotised areas between arms. Posterior circlet with over 350 rows of up to 55 hooks (n = 6). Anal gill trilobed, each lobe with 15-22 fine finger-like lobules of which one is slightly larger than remainder (n = 6).