ote all 
121 
one, which is uncommonly thick and elevated. This very fine species 
is distinguished by many peculiarities from all others I am acquainted 
with. 
6. Dostn1A sPECULARIS, Romer. D. testa subcordato-orbiculart, 
vir altiore quam longa, postice obtuse angulata, tumida, solida, 
valde inequilaterali ; concentrice tenui-striata, striis planis, 
densis, ad latera furcatis, elevatioribus et in lamellis brevibus, 
precipue postice terminatis ; strigillis longitudinalibus interruptis, 
irregularibus, extremitates versus evanescentibus ; sordide alba ; 
umbonibus pallide luteis, valde prominulis, recurvisque, in } lon- 
gitudinis collocatis ; margine ventrali semicirculari, antice et 
postice valde adscendente ; dorsali antico perbrevi, concavo, postico 
macime declivi, longe curvatim descendente ; lunula late cordata, 
impressa, plana, circumscripta ; area lanceolata, profunde exca- 
vata, longitudinaliter strigillata, marginibus acutis, lamellis brevi- 
bus limitatis ; ligamento immerso, vix conspicuo ; pagina interna 
alba; sinu palliari mediocri, triangulari, apice acuto, lineis sub- 
rectis incluso, linea superiore horizontali; dente laterali incras- 
sato, secundo cardinali in valva sinistra crassissimo, irregulariter 
plicato, reliquis tenuibus. 
Long. 28, alt. 29, crass. 16 mill. 
Hab. Malacca. 
In general appearance like D. adansonii of Philippi (which is 
neither Le Dosin of Adanson, nor D. africana of Gray), but a 
thicker and more oblique shell, having the concentric strize lamellar 
at the sides, whilst in D. adansonii they are uniformly flat; the 
ligament-area is more excavated in D. specularis than in the latter, 
and the pallial sinus is shorter and forms an acute angle, being in 
D. adansonii rounded in the apex. The scar of the posterior muscle 
is uncommonly small and nearly circular. 
7. Dostn1a RustTICA, Romer. D. testa ovato-orbiculari, longiore 
quam alta, postice distincte anguluta, tumidiuscula, valde inequi- 
laterali; liris transversalibus, subdensis, inequalibus, elevatis, 
sublamellosis, antice posticeque in lamellis tenuibus mutatis, 
scabra; sordide alba; umbonibus tumidiusculis, su®prominulis, 
satis antrorsum recurvatis, in 2 longitudinis positis ; margine ven- 
trali semicirculari, postice vix producto, antice rotundato et 
valde adscendente ; margine dorsali antico brevi, concavo, postico 
valde declivi, curvatim longe descendente ; lunula cordata, im- 
pressa, circumscripta, subplana, longitudinaliter striata ; area 
late lanceolata, subexcavata, strigillata ; ligamento immerso, vir 
conspicuo ; intus albida, medio ferrugineo maculata ; sinu palliari 
mediocri, triangulari, haud aperto, apice obtusiusculo, lineis sub- 
concavis incluso, superiore fere horizontali ; dente laterali crasso, 
apilliformi. 
Long. 28, alt. 26, crass. 14 mill. 
Hab. ? 
The outline is that of D. aspera, Reeve, which is a smaller shell 
