1894. 



PROCEEDINGS OF THE NATIONAL MUSEUM. 691 



smaller than tbe other, and its valve or orifice iu the alcoholic speci- 

 men does not project iiiterually; both are surrounded with about the 

 same relative amount of papillae, which seem to be of about the same 

 series of sizes for each orifice. The intestinal canal passes over the 

 posterior adductor and terminates near the excurrent siphon, internally, 

 but has no projecting free portion. 



The outer lamina of the mantle when removed from the shell shows a 

 band of short fibers less than 2 mm. in length and diminishing down- 

 ward; they extend anteriorly from the mantle margin, and are disposed 

 over the space in front of the siphonal area from the adductor above 

 downward as for as the area extends. These are, without doubt, the 

 retractor muscles of the siphons, and correspond to the slight concave 

 curve below the adductor scar, which may be traced in the pallial 

 impression. The mantle is remarkable for its large blood sinuses, and 

 the pericardium is unusually large, as well as the ventricle of the heart. 

 The latter is a thin, semitranslucent pear-shaped sac, dorsal to the rec- 

 tum and not pierced by it. It is slightly asymmetrical, lying a little 

 more to the right on the median line. The auricles enter the base 

 laterally, being set oif by a marked constriction, and are muscular and 

 of a darker color than the ventricle, apparently having a thin glandu- 

 lar coating. Laterally from each auricle a funicular muscular tube 

 extends to a capacious sinus in the wall of the mantle. There is a 

 single anterior aorta starting from the base of the ventricle. The peri- 

 cardium and its contents lie behind the cardinal teeth and beaks. The 

 visceral mass below the latter seems but moderately supplied with 

 hepatic lobules, and, superficiall3% exhibits the ramifications of the 

 ovary. The male glands are lower down and of a pale color. The foot 

 resembles that of Verticordia iu being somewhat constricted above, 

 but is much more like that of the average pelecypod. It is pointed and 

 produced moderately iu front, cou)pressed, the lower part somewhat 

 keeled, the posterior more swollen, with a slight "heel," and no trace 

 of a byssal groove or gland. The retractor muscles of the foot form a 

 slender, solid cord below, which ascends and bifurcates behind the 

 middle of the shell and is attached on each side above the main body 

 of the adductor, but forms an almost indistinguishable part of the 

 same imi^ression on the shell. The protractors, however, make sepa- 

 rate scars a little behind and above the anterior adductor scar. 



Eeversing the animal and separating the lobes of the mantle, we 

 find the foot closely embraced above by the ctenidia, which extend 

 forward and are attached firndy to the mantle at their outer edges, and 

 anteriorly reach to a point close to and just outside of the ventral pair 

 of palpi. In looking down upon the reversed animal the most anterior 

 part of the ctenidia is concealed by the foot and palpi. Leaving a fuller 

 description of the giJl until later, attention may be directed to the 

 parts about the mouth. Just behind the anterior adductor are 

 perceptible two or more i^ouch like sacs on each side in front of the 



