RECENT BRITISH OSTRACODA. 



4-55 



Genus 13. Sclerochiltjs, G. O. Sars. 

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

 shining, ornamented with very minute scattered papillae. Hinge-joint formed by a pro- 

 jecting median crest of the left valve. Antennae robust; second joint of the upper 

 bearing a seta on the anterior and posterior margins, the last five joints quickly 

 decreasing in size and bearing numerous long setae ; lower antennae larger than the 

 upper, 5-jointed; flagellum long and very slender. Poison-glands very large, and 

 divided into many lobes. Mouth produced, conical; labrum strongly toothed. Man- 

 dibles small ; teeth numerous and acuminate ; palp narrow, indistinctly 3-jointed, with 

 a distinct branchial appendage. Terminal lobes of the first pair of jaws partly wanting ; 

 branchial plate narrow, almost lanceolate, and set with numerous setae on the outer and 

 inner margins. Peet short and robust; second and third joints armed in front with a 

 short seta ; first pair armed with a single strong spine at the apex of the basal joint. 

 Postabdominal lobes larger than usual, forming broad bilobed laminae, and bearing five 

 setse. Eye single. 



In outward appearance the one species belonging to this genus is scarcely separable 

 from the following [Faradoxostoma) ; but the structure of the animal shows an apparent 

 transition from the Cythere type to that of JParadoxostoma. This is more especially 

 evident in the mandibles and mouth. 



ScLEHOCHiLUS CONTORTTJS, Norman. (Plate XXXIV. figs. 5-10, and Plate XLI. fig. 7.) 



Cythere contorta, Norman, Ann. & Mag. Nat. Hist. vol. ix. 186.2; p. 48, pi. ii. fig. 15; and Trans. Tyne- 



side Nat. Field Club, vol. v. p. 150, pi. iii. fig. 15. 

 Sclerochilus contortus, Gr. O. Sars, loc. cit. p. 90. 



British type. Distribution : Recent — Britain, Norway, Bay of Biscay. Fossil — Glacial and raised 

 beaches, Scotland, Ireland, Norway. 



Carapace of the female, seen from the side, elongated, bean-shaped, higher behind than 

 in front ; greatest height rather behind the middle, and equal to considerably less than 

 half the length. Anterior and posterior margins rounded ; superior boldly arched, 

 sloping steeply in front, inferior deeply sinuated in front, convex behind. Outline, as 

 seen from above, compressed oval, more than twice as long as broad ; greatest width 

 behind the middle, tapering to the extremities, the anterior of which is the more acutely 

 pointed. Shell of the male more elongated, the dorsal margin less convex. Shell smooth 

 and polished, very sparingly punctate, the margins marked watli short transverse, 

 radiating striae. Colour yellowish, with a reddish-brow^n patch on the dorsum. Lucid 

 spots five, Knear-oblong, parallel. Third joint of the upper antennae not shorter than 

 the preceding, and about equal to the united lengths of the three following. " Branchial 

 appendage of the mandibular palp bearing four long, subequal setae." Pirst pair of jaws 

 having only two terminal lobes, one of which is very narrow, and terminated by a hooked 

 spine. Second joint of the last pair of feet shorter than the two following. Basal 

 portion of the male copulative organs semiovate ; upper and anterior margin forming a 

 continuous arch ; distal portion smaller, subovate, narrowed to the base. 



Length J3 in. , , 



