The anatomy of _Aspergillum_ is similar to that of _Pholas_; its mantle, however, is all but closed in front, and ends in an obliquely-set muscular disk, applied to the internal surface of the rose of the so-called _arrosoir_, the openings of this part of the shell giving exit to certain processes and fimbriæ of the fleshy disk,--a narrow slit being also left in both the muscular and shelly disks for the exsertion of the small, compressed and curved foot. The animal is enveloped within the shell by a rather horny, general membrane. The author touches upon the anatomy of some other genera of Lamellibranchiata. _Solemya_ has its firm, horny, dark cuticle doubled inwards from the valves over the tubular mantle; behind, it has an anal opening, and a second fringed branchial slit lower down: the branchiæ and tentacles are single on each side, the former being remarkably feather-like. The foot is similar to that of the Solens, but crenate round its anterior disk. _Cyrenoidea_ has the mantle closed below, but with two openings behind, the upper one with a semicircular internal fringe, incomplete above; a callous rim and fringe surround the mantle, which has also a third opening for the long, compressed, bent, and blunt foot. This last has a remarkable crystalline body, directed from the stomach to the pedal pore, apparently, as in _Cardium_, subserving by its elasticity to the extension of the foot, and consequently to locomotion; at any rate, it is not a sexual distinction. The external branchiæ are short, and the upper or internal branchial cavity does not communicate with the lower one. The renal organ opens near the branchial nerve, and the ovary at the base of the abdominal mass. _Trigonia_ is remarkable for its beautifully fringed, open mantle, its pectinated pits for the secretion of the teeth, and the large scythe-shaped foot, trenchant before and peaked behind, and having a fringed disk. _Vulsella_ is allied to the Oyster, but more so to the Pectens, having a small cylindrical grooved foot and appended visceral mass, but no byssus; the rectum perforates the heart, and has a tentacle above its opening. _Perna_ has a similar foot, and a very bulky byssus, with a large muscle attached to their base; the lips resemble those of the Oyster. The anatomy of _Crania_ is little different from that of _Orbicula_, as described by Owen,--the beautiful arms folded in several coils, with a simple mouth at their base, the stomach and short intestinal canal surrounded by the liver and hearts, and terminating by a lateral bend; the ovaries ramifying in the mantle; the adductor muscles being four in number, with some bands to the mantle; and on the latter, glandular markings corresponding with the microscopic sculpture of the shell. With respect to _Anomia_, the author has again been anticipated by Lacaze-Duthiers, though he has already given, in another paper, most of its anatomy and morphology: he would simply call