MK. E. GARNER ON THE SHELL-BEARING MOLLUSCA. 37 



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 branchiae 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 branchiae are 

 short, and the upper or internal branchial cavity does not commu- 

 nicate 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 beauti- 

 ful 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 cor- 

 responding 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 attention to 

 its very long and curious crystalline stilette, unconnected with the 

 minute foot. 



With respect to that qucestio vexata, the sexes of the Lamelli- 



