ItACTEA.— Plate XVIII. 



matis ; area, elongato-ovatd, lunuldque tenuistriads ; 

 cardine aiiffiislo,fossiiM profiiudd ; dentibus latendi- 

 bus lamellosis, prominentibm, autico midto breviore ; 

 sinu pallii laio, vix excavato. 



The attenuated Mactra. Shell ovately triangular, 

 transverse, thin, swollen, inequilateral, transversely 

 irregularly thickly striated, livid-violet, blackish-violet 

 at the umboes, paler violet within, anterior side the 

 shorter, obtuse, slanting at the upper part, posterior 

 side slanting, truncated ; umboes short, a little ob- 

 lique, approximated ; area elongately ovate, and witii 

 the lunule finely striated ; hinge narrow, pit deep ; 

 lateral teeth lamellous, prominent, the anterior much 

 the shorter ; sinus of the mantle broad, scarcely ex- 

 cavated. 



Deshayes, Pro. Zool. Soc. 1854. 



Rab. ? 



Of a peculiar dark livid ash-violet colour within and 

 without, somewhat unusually attenuated towards the pos- 

 terior extremity. 



Species 98. (Mus. Cuming.) 



Mactra coebiculoides. Mad. testa tngono-subqua- 

 dratd, crassittscidd, turgidd, submquilaterali, livido- 

 albidd, ad umboHes intense caruled, latere antico ro- 

 tmidato, postico concavo-rostrato j lunula aredque 

 magnis, latis, suhconcavis ; umlonibus tumidis, ap- 

 proximatis, intus intense caruleo-violaced. 



The little basket Mactra. Shell triangularly sub- 

 quadrate, rather thick, swollen, nearly equilateral, 

 livid white, deep blue at the umboes, anterior side 

 rounded, posterior concavely beaked ; lunule and area 

 large, broad, subconcave ; umboes swollen, close, in- 

 terior deep blue-violet. 



Deshayes, Pro. Zool. Soc. 1854. 



Hab. Ceylon ; E. L. Layard. 



A short triangularly gibbous species, rather thick, deep 

 blue-violet at the umboes, and especially deep-dyed with 

 the same colour in the interior. 



Species 99. (Mus. Cuming.) 



Mactra lateralis. Mad. testd trigono-ovatd, inaqvi- 

 laterali, fransversim subirregular'Uer sidcato-striatd, 

 squalidi albd, epidermide fuscescente partim indutd, 

 latere antico brevi, obtuse unyulato, postico attenuato. 



subrostrato ; lunula aredque subamplis, dense striafis ; 

 umbonibus angulatis, approximatis. 



The lateral Mactra. Shell triangularly ovate, inequi- 

 lateral, transversely rather irregularly groove-striated, 

 dirty-white, partially covered with a brownish epi- 

 dermis, anterior side short, obtusely angled, posterior 

 attenuated, somewhat beaked ; lunule and area rather 

 large, closely striated; umboes angular, approximated. 



Say, Jouni. Acad. Nat. Sci. Philadelphia, vol. ii. p. 309. 



Hab. Massachusetts, United States ; Gould. 



\ simple triangularly ovate species, of a stone-white 

 hue, attenuately produced at the posterior end. 



Species 100. (Mus. Cuming.) 



Mactra incongrua. Mact. testd trigond, gibbosd, sub- 

 cequilaterali, tewuiculd, lavigatd, calcareo-albd, lateri- 

 bus obtuse angulatis, postico subproducto ; lunuld ared- 

 que ovatis, latiusculis, eleganter plicato-striatis ; utn- 

 honibus appro.vimaiis. 



The incongruous Mactra. Shell triangular, gibbous, 

 nearly equilateral, rather thin, smooth, chalk-white, 

 sides obtusely angled, the posterior rather produced ; 

 lunule and area ovate, rather broad, elegantly pli- 

 cately striated ; umboes close. 



Deshayes, Pro. Zool. Soc. 1854. 



Hab. Island of Luzon, Philippines ; Cuming. 



The chief peculiarity of this species, consists in the lu- 

 nule and area being elegantly plicately striated, while the 

 rest of the shell is smooth. 



Species 101. (Mus. Cuming.) 



Mactea elliptica. Mact. testd trigono-ellipticd, com- 

 pressd, crassinsculd, subcequilaierali, transversim rude 

 plicatd et striata, lateribus rotundatis, antico sublon- 

 giore ; Immld aredque angustis, indisiindis ; ttmboni- 

 bus minimis, approximatis. 



The elliptic Mactra. Shell triangularly elliptic, com- 

 pressed, rather thin, nearly equilateral, transversely 

 rudely plicated and striated, sides rounded, anterior 

 rather the longer ; lunule and area narrow, indistinct ; 

 umboes very small, close. 



Bkown, Ulus. Conch. Brit. p. 109. pi. 41. f. 6. 



Hab. British and French Soas. 



A rather solid rudely plicated compressed shell, with 

 the anterior side rather the longer, the umboes being very 

 small and the lunule and area not verv distinct. 



