304 MAZATLAN UNIVALVES 
304. VERMETUS EBURNEUS, Rve. 
V. t. alba, seu rubro-fusco tinctd, satis magna ; anfr. spirali- 
bus albis x.-xiv.; primis iii. valde rotundatis, levibus ; dein 
caring und acutd, dein duabus, postea tribus monstrantibus, 
quarum una circa peripheriam major ; postea subito irregulart, 
aifr. separatis, vix spiralibus, marginibus plerumque valde 
dwergentibus, parum seu ad sese, seu ad concham alienam 
affixis ; spiraliter tenué et confertim striata, costis interduin 
subobsoletis ; adultd interdum rufo-fusco tinctd. 
Operculo extus concavo ; foliis plurimis tenuibus alterd intus 
alieram siti; radiatim tenuissime striulato, strinlarwin inter- 
stitiis punctulatis ; intus marginem versus convexo, opaciore, 
margine tenuissimo ; eicatrice circulart, trienti latitudinis haud 
aquante, lirulis circiter xii. concentricis ornato. 
Proc. Zool. Soc. 1842, p. 197:—Conch. Syst. vol. ii. p. 46, 
pl. 152, f. 2. 
Comp. Vermetus pellucidus, Brod. § Sow. Zool. Journ. vol. iv. 
1829, p. 369. “V.t. pellucidd, longitudinaliter striata, apicem 
versus carinatd.” (This description will suit the young of 
V. eburneus, but is not sufficiently explicit for certainty.) 
The operculum is described from specimens in Mr. Cuming’s 
collection, which are believed to be authentic, as they agree 
with that of V. Hindsii in the B. M., though differing essentially 
from the figure professing to be of that species in H. & A. Ad. 
Gen. pl. 38, f. 8, a, 5. An operculum agreeing even in the 
peculiar microscopic markings is seen in Mus. Cum, in a very 
different shell, which has lost its apex, but is probably an 
Aletes, and s not unlike A. squamigerus. The V. Hindsii 
seems to diffeir from V. eburneus in the arrangement of the 
keels on the turriteHoid portion. 
About 30 young specimens of this very beautiful species 
were obtained on Chame and Spondyli; but only two were 
found adult, loosely entwined on a Chama. ‘These, having 
passed through the acid process, have lost their sculpture and 
would hardly be known from A. centiquadrus, (with which 
the later whirls agree in colour,) but for the Turritelloid 
apices, which have fortunately survived. ‘The sudden contrast 
between the elegantly chiseled, alabastrine Pseudo-Turritella, 
and the irregular, almost smooth subsequent whirls, is very 
remarkable. A fossil species found by Mr. Nuttall at New- 
burn, N. Carolina, differs essentially from the Atlantic species, 
and offers no marks by which it has been distinguished from this. 
