RErORT ON THE OSTRACODA. 147 



Dredged off Heard Island, in a depth of 75 fathoms. Mud. (Station 151.) 

 [PI. XXXV. fig. 6, a-d. a Carapace seen from left side, b from above, c from l^elow, 

 d from front. Magnified 50 diameters.] 



Sclerochilus, G. 0. Sars (1865). 



Valves elongated, very hard, especially towards the margins ; surface smooth and 

 shining, ornamented with minute scattered papillse. Hinge-joint formed by a projecting 

 median crest of the left valve. Muscle-spots linear, subparallel, arranged in an oblique 

 oval patch below the centre of the valve. Antennae robust ; the anterior bearing on 

 each side of its second joint a single seta, its last five joints successively smaller, and 

 bearing numerous long setae ; posterior antennae larger tlian the anterior, five-jointed, 

 flagellum very long and slender. Poison-glands very large, and divided into several lobes. 

 Mouth produced, conical ; labrum strongly toothed. Mandibles small, teeth numerous 

 and sharp ; paljj narrow, indistinctly three-jointed, and having a distinct branchial ap- 

 pendage. Terminal lobes of the first pair of jaws partly wanting ; branchial plate narrow, 

 almost lanceolate, and beset with numerous setse on the outer and inner margins. Feet 

 short and robust, second and third joints bearing in front a sharp seta ; first pair armed 

 with a single strong spine at the apex of the basal joint. Post-abdominal lobes 

 larger than usual, forming two broad bilobed laminae, each bearing five setae. Eye single. 



To this genus we can with certainty refer only the single species here noticed ; a 

 species which is, however, generally distributed on the Atlantic shores of Europe, reaching 

 as far north as Spitzbergen. It occurs abundantly in almost all the Post-Tertiary beds 

 of Great Britain and Ireland, as well as in those of Norway and Canada. 



1. Sclerochilus contortus (Norman), (PL XXXV. fig. 8, a, h). 



Cythere contor-ta, Norman, Ann. and Mag. Nat. Hist., vol. ix. p. 48, pL ii. fig. 15 ; Trans. Tyneside 



Nat. Field Club, vol. v. p. 150, pi. iii. fig. 15 (1862). 

 Sclerochilus contortus, Sars, Oversigt. Norges marine Ostrac, p. 90 (1865). 



Sclerochilus contortus, Brady, Mong. Eec. Brit. Ostr., p. 455, pi. xxxiv. figs. 5-10, and pi xlL fig. 7. 

 Sclerochilus contortus, Brady, Crosskey, and Robertson, Monog. Post-Tertiary Enfcom., p. 212, 



pi. X. figs. 33-35. 



Carapace, as seen from the side, elongated, bean-shaped, higher behind than in front, 

 height equal to about half the length ; extremities well rounded, dorsal margin boldly 

 arched, inferior deeply sinuated in front of the middle ; seen from above, compressed, 

 ovate, extremities acutely pointed, width scarcely equal to one-third of the length ; end 

 view ovate, rounded above, pointed below. Shell perfectly smooth. Length, l-33d of 

 an inch ("77 mm.). 



Several specimens, all consisting of separated valves, were found in dredgings from 

 Balfour Bay, Kerguelen Island, 20-50 fathoms ; from off Heard Island, 75 fathoms ; 

 from Wellington Harbour, New Zealand (in tow-net at trawl). 



