144 MR JAMES COSMO MELVILL AND MR ROBERT STANDEN ON THE 



ephippium. We are corroborated in our opinion by its having been noted in the 

 Tristan d'Acunha group (Nightingale Island) during the Challenger Expedition.* 



Sub-order arcacea. 

 Family Arcadse. 



Area (Bathyarca) strebeli, sp. n. (Plate, figs. 13, 13a). 



A. testa parva, orbiculata, paullum inaequilaterali, aequivalvi, alba, epidermide tenui, olivacea, fibrosa, 

 praedita, radiatim tenuissime" arctilirata, lineis concentricis incrementalibus irregulariter cancellata, latere 

 antico abbreviate, postico late rotundato, margine dorsali fere recto, deinde marginem apud ventralem leniter 

 rotundato, umbonibus prominulis, obtusis, contiguis, conspicuis, dentibus parvis ad 18, pagini interna alba, 

 marginibus lsevibus. 



Alt. 4 "5, lat. 5, diam. 4 mm. 



Hab.— Trawl, Station 291, lat. 67° 33' S., long. 36° 35' W., 2000 fathoms 

 March 7, 1903. 



Allied to A. inaequisculpta, Sm. [Rep. "Challenger" Exp., xiii., p. 267, pi. xvii., 

 figs. 8-8c), but differing from that species and its allies, A. pectunculoides, Scacchi, 

 A. frielei, Jeffreys, and A. anaclima, Melv.,t in its rounder outline, more prominent 

 umbones, and greater delicacy of texture. It is slightly larger than A. imitata, Sm. 

 (I.e., p. 321, figs, in text), which seems a very variable form, dredged in the North Pacific 

 Ocean, lat. 35° 22' N., long. 169° 53' E., at 2900 fathoms. This last is a coarser shell 

 than A. strebeli, but its nearest congener, in our opinion. It gives us pleasure to 

 connect with this interesting benthal species the name of Dr Hermann Strebel, who 

 was good enough to examine it, and give us his opinion concerning it. 



Lissarca notorcadensis,\ sp. n. (Plate, figs. 14, 14a). 



L. testa parva, rotundo- vel ovato-trapezoide, solidiuscula, sordide" alba, asquivalvi, inaequilaterali. 

 interdum epidermide fugaci, tenui, olivacea, pallida, partim tecta, undique concentrice arete striata, 

 umbonibus obtusis, fere contiguis, ligamento partim externo, antice angusta, postice" expansa, marginem 

 ad ventralem rotundata, pagina interna alba, laevigata, marginibus pulchre" crenulatis, dentibus ad 10, 

 utrimque divergentibus. 



Alt. 5, lat. 6, diam. 2 - 75 mm. 



Hab. — Off weed, and attached to Bryozoa, etc., Station 325, Scotia Bay, South 

 Orkneys, 9-15 fathoms; also in same bay, April-June 1903, June 1904. 



A proportionately thick, smoothish, white Lissarca ; some examples roundly, others 

 (and more generally) ovately trapezoid ; larger as a rule than L. rubrofusca, Smith, 

 which was found with it. The whole surface is closely concentrically striate. Within, 

 the margins are crenulate ; the teeth, five on each side of the hinge-plate, divergent. 



Lissarca rubrofusca, Smith. 



Lissarca rubrofusca, E. A. Smith, Phil. Trans. Royal Soc. (1879), vol. clxviii., p. 185, pi. ix. 

 fig. 17. 

 ,, ,, E. von Martens and G. Pfeffer, Mollusken von Sud-Georgien, 1886, p. 128, 



Taf. iv., fig. 14 a-e. 



* Rep. "Challenger" Exped., xiii., p. 318. t Proc. Zool. Soc. Lond. (1907), i., p. 794, pi. liv., fig. 6. 



\ v6Tos"OpicaS(s, from the locality. 



