Hydroniscus buzwilsoni George 2004, n. sp.

Hydroniscus buzwilsoni n. sp.

(figure 12)

Diagnosis. Hydroniscus with a large rounded spatula-like projection on the frontal margin of the cephalon. Lateral margin of pereonites parallel. Lateral sutures prominent between pereonites 1–5. Posterior three pereonites and pleotelson fused middorsally to form a single somewhat quadrate segment. Posterolateral projections of pleotelson and apex in line with the tip of the uropods. Antenna 1 with a short basal peduncular article and an elongated second peduncular article, flagellum of five articles. Antenna 2 with a peduncle of five articles and a flagellum of 11 articles.

Material examined. Holotype: male, length 3.1 mm, maximum width 1.2 mm. USNM Cat. No. 138670.

Type locality. R / V Eastward Sta. 5809, site Beta over the Carolina lower slope.

Etymology. This new species is named in honour of the Australian isopodologist Dr George Wilson of the Australian Museum of Natural History, Sydney.

Description. Body broad, with lateral margins straight and somewhat parallel. Cephalon with a prominent and broad spatula-like rostral lobe. Lateral sutures between pereonites 1 and 5 well-defined. Lateral lobes of pereonites fringed with minute setae. Second pereonite longer than the first. Pereonites 2–4 subequal. Pereonites 5–7 fused mid-dorsally with pleotelson to form a single consolidated segment. Posterolateral projections of pleotelson small, separated widely by the rounded posterior margin of the pleotelson.

Antenna 1 basal peduncular article very short, less than one-quarter the length of the elongated second peduncular article. Flagellum of five articles, terminal article with a pair of long aesthetascs and a long seta. Antenna 2 with peduncle of five articles; basal article extremely short, articles 2 and 3 subequal, article 4 more than twice length of article 2, and article 5 about the same length as article 4 but narrower. Maxilliped endite with three coupling hooks, palp of five articles, basal article of palp less than half length of article 2, terminal article with a tuft of long setae.

Male pleopod 1 broad with narrow apex, distal lobes extending laterally to an acute tip. Anal chamber well-separated from branchial cavity where the pleopods are lodged. Uropods reduced, reaching the tip of the small posterolateral projections of the pleotelson.

Remarks. This new species is similar to H. ornatus Menzies, 1962 from the south Atlantic off the coast of Brazil and H. vitjazi Birsten, 1963 from the north-west Pacific in having a broad rostral lobe. The posterolateral projections are rather close with a narrow posterior margin of pleotelson in H. vitjazi, but the posterior margin of the pleotelson is well-separated between the posterolateral projections in both H. ornatus and H. buzwilsoni n. sp. Nevertheless, this new species is clearly distinguished from H. ornatuts which has the anterolateral angles of pereonite 5 produced to half the length of the lateral margin of pereonite 4.