18 
spot, which is situated just on the margin of the shell, where the 
exterior stripe terminates. 
TELLINA (subg. ARgopacia) SIAMENSIS, mM. 
Testa ovata, compressa, subequilateralis, lamellis concentricis con- 
fertis et striis radiantibus decussata, antice rotundata, postice 
carinata, lumellis distantioribus, magis elevatis, sulcis im- 
pressis 2 ante carinam sculpta ; flavescenti-alba, haud nitens ; 
margo ventralis modice arcuatus, postice valde ascendens et 
subinde subsinuatus ; dentes cardinales valve dextre duo, pos- 
terior bifidus, valve sinistre duo, prior bifidus, posterior parvus ; 
dentes laterales in utraque valva anticus et posticus distincti, 
triangulares, a cardinalibus remoti ; facies interna alba, sinus 
palliaris maximus. 
Long. 49, alt. 33, diam. 14 mill. ; vertices in $ longitudinis siti. 
This shell is allied to Tellina capsoides, Hanley, and 7’. concen- 
trica, Gould, but it can at once be distinguished by its form being 
transversely ovate and nearly equilateral, like that of 7. pristis. 
CAPSELLA VIOLACEA, Reeve? 
The Siamese shell is rather stronger than is usual in this species; 
long. 63, alt. 31, diam. 19 mill. ; vertices in # long. 
SOLETELLINA TRUNCATA, Gmel. ? 
I have seen only a worn specimen, the end of which was less 
truncate than is usual in this species ; Mr. Cuming therefore thinks 
it distinct. 
4. Descriptions oF New Species or MOLLUscA FROM THE 
Sanpwicu Istanps. By W. Harper Pease. (Commvu- 
NICATED BY Dr. J. E. Gray.) 
Before commencing my descriptions, I should remark that I call 
the hinder part of the shell (near the apex) the posterior end. 
Being accustomed to see the animal in connexion with the shell in 
motion, it appears to me unnatural to call the mouth posterior and 
the apex anterior, as some authors do. 
I begin with the Opisthobranchiates, the Bullide, and so on 
through the Nudibranchiates. There is no part of my collection 
with which I am so little acquainted as the Bullide, having received 
but few specimens for comparison, and therefore relying mostly on 
descriptions for the determination of species. I am often misled 
by these, in such cases, for instance, as where an author makes use 
of the term s¢rie to mean raised lines, having always considered 
that s¢rie indicate quite another character from raised lines. Again, 
descriptions are drawn up from imperfect specimens, and are copied 
into monographs without alteration or correction. 
Of Bullina vitrea I have lately procured the two largest and most — 
