150 
being much diminished after the loss of locomotion, the branchial 
apparatus does not merely present an atrophied state of its usual 
structure in the free Calyptreide, but a different condition of that 
structure,—two very short gills replacing one very extensive one, 
and the form of the branchial filaments being quite different,—the 
conclusion seems unavoidable, that the Litheduphus is a good and 
constant genus, created with reference to that peculiar mode of life 
to which its bivalve shell and other generic characters as a Calyp- 
treidan are correlated.” 
The next paper read was also from Prof. Owen, and contains an 
account of the anatomy of the Pholadomya candida. The genus 
Pholadomya was founded by G. B. Sowerby, upon certain peculiarities 
observable in the structure of a shell which in some of its characters 
approaches the genera Solen, Pholas, and Mya. ‘The animal exhibits 
the ordinary characters of the Acephala inclusa of Cuvier, being 
everywhere shut up in a mantle which gives issue only to the siphonic 
tube and the foot; it presents, however, in addition to the pedal and 
the two siphonic apertures, a fourth orifice, at the under part of the 
siphon, which is of small size and circular form. This orifice alone, 
observes Prof. Owen, is sufficient to distinguish the present mollusk 
from any known genus of the Inclusa. It would seem to be an inlet 
for respiratory currents, supplementary to the ordinary ventral siphon. 
The animal, compared with that of the Panopea australis, the cha- 
racters of which are detailed by M. Valenciennes, is distinguishable 
not only by an accessory bifurcate foot and valvular aperture, but 
by its undivided branchize and some other less marked characters ; 
nevertheless the affinity to Panopea, as indicated by the hinge of the 
shell, is illustrated by a closer general resemblance of its soft parts 
to that genus than to Mya, Solen, or Pholas. These two papers, 
from the pen of Prof. Owen, and of which the above is a brief abs- 
tract, are illustrated with beautifully executed drawings. 
Dr. Pfeiffer’s descriptions of new species of Shells collected by 
H. Cuming, Esq. in the Philippine Islands, were then read. 
Heurx cromyoprs. Hel. testd imperforatd, depresso-globosd, 
tenuissimd, pellucidd, olivaceo-fulvd, apice violaced; anfractibus 
4 planiusculis, ultimo magno, medio fascid latd albd cingulato et 
epidermide tenuissimd cinerascente fasciatim ornato ; columella 
perobliqud, latd, alba ; apertura lunato-ovali; peristomate sim- 
plicit, expanso, margine rufo-violascente. : 
Diam. 14 poll. ; altit. 103 lin. : 
Hab. Cagayan, province Misamis of the island Mindanao. Found 
on leaves of trees. 
Hexix taneurwa. Hel. testd imperforatd, globosd, tenuiusculd, 
regulariter et confertim oblique striatd, apice obtuso lutescente, un- 
fractu ultimo rufo, epidermide hydrophand cinerascente indutd, 
albo-lineolatd, basi nudo, nitido ; suturd lined fused nitidd, notatd ; 
anfractibus 45 conveviusculis ; columelld verticali, albo-callosd ; 
aperturd subovali ; peristomate .... ? 
