1890.] MARINE MOLLCSCA OF ST. HELENA. 313 



II. PELECYPODA. 



Saxicava arctica (Linn.). 

 Hab. Cosmopolitan. 



Kellia crassiuscula. (Plate XXIV. fig. 23.) 



Testa glohosn, rotunde ovata, nitida, alba, apices versus suhpellucida, 

 concentriee subrugose striata, fere cequilateralis ; latus anticum 

 posteriore paulo anr/mtius ; pa7^?lrt interna alba, incrassata, 

 minute subruffosa ; linea cardinalis crassiuscula, dente veltuber- 

 culo cardinali et laterali posteriore tuberculari in utraque valva 

 instructa ; ligamentum internum pone umbones situm. 



Longit. 63- millim., alt. 5, diam. 3|. 



For a shell of such small size it is rather thick. The umbones 

 are only very slightly elevated, curved towards the anterior end, and 

 capped at the tip with a minute embryonic shell. 



Kellia atlantica. (Plate XXIV. fig. 24.) 



Testa minuta, ohlongo-rotundata, inasquilateralis, sordide albida, 

 concentriee tenuissirne striata; margodorsianticusvaldedeclivis, 

 leviter convexus, posticus longior, subJiorizontalis ; latus anticum 

 acute rotimdatum, posticum latius excurvatum ; margo inferior 

 late arcuatus. Dens cardinalis valvce sinistrtv ^-formce, valvce 

 dextrce unicus prominens, acutus ; dens lateralis posticus in 

 utraque valva elongatus, in dextra validus, margine dorsali sulco 

 separatus. 



Longit. 2^ millim., alt. 2, diam. 1|. 



This species is about the size of Lepton clarJcics, but not of the 

 same form. 



MONTACUTA SUBTRIANGULARTS, (Plate XXIV. fig. 25.) 



Testa fere cequilateralis, mediocriter convexa, sordide albida, haud 

 nitida, rotunde subtriangidaris, lineis incrementi striata, postice 

 quam antice paulo angustior ; margo dorsalis utrinque declivis, 

 postice vix exeurvatus, antice leviter concavus, ventralis rectus vel 

 in medio levissime incurvatus ; umbones prominuU, subacuti ; 

 pagina interna nitida, prope margine incrassata; cicatrices 

 magnce, subpyriformes ; dentes duo valvce sinistrce prominentes, 

 divergentes. 



Longit. 4| millim., alt. 3g, diam. 2|. 



This species has the dorsal margin sloping on each side and the 

 base almost straight, so that a somewhat triangular shape is produced, 

 the two lower angles being well rounded. 



LuciNA (Codakia) imbricatula, C. B. Adams. 



Lucina imbricatula, C. B. Adams, Proc. Boston Soc. Nat. Ilist. 

 1845, vol. ii. p. 10 ; id. Contrib. Conch, p. 24.'). 



