230 BULLETIN OF THE 
cartilaginous consistency, in others they were soft like ordinary tissue; the 
other end of the intestine passes over the posterior adductors firmly knitted 
to the fascia by connective tissue and having two thin broad bands of muscle 
parallel with it which seem adapted to give some voluntary motion to the 
free end of the intestine, which projects 10.0 mm. beyond its attachments, near 
its end is deeply constricted, and ends in a small round centrally pierced but- 
ton-like expansion. The diameter of the terminal button is about 0.37, of the 
constriction 0.25, of the internal tube about 0.25, and the average of the free 
part of the intestine 0.5-0.7 mm. The diameter of the tube is somewhat 
irregular, and it contained, in the specimens examined, more or less dark gray 
fecal matter. In the structure of the two ends of the alimentary canal this 
mollusk resembles Trigonta and some Pectinide. The liver presented differ- 
ent appearances in different specimens; in younger but pretty well developed 
examples it presented the appearance of a number of free simple deep olive- 
green tubules radiating from a comparatively small plexus as a centre, through 
which passed the intestine ; in older specimens it had acquired a more solid 
and compact consistency, the single tubules were no longer recognizable, the 
interior was brownish when cut, and the outer surface was ornamented with 
a few whitish dendritic branches extending over it from the generative glands 
below the liver; the mass of the ovaries or sperm glands occupy part of an 
irregular space behind the mouth and in front of the posterior adductors, the 
liver projects into it beneath its surface in the median line, its lower external 
surface is keeled, but a foot is not developed; the substance of the ovary is 
disposed in, proportionally, rather large ramifications, with acorn-shaped* 
lobules containing granular cream-colored matter irregularly distributed on 
the inner surface ; the supposed male gland was similar, but the contents were 
of a finer consistency and of a more greenish color. The texture of all the 
viscera is extremely loose and delicate, and their disposition differed in minor 
details in all the animals examined. This might be partly owing to the vio- 
lence necessary, even with the greatest care, to open the valves so that the 
soft parts could be examined, and the extreme delicacy of the visceral tissues. 
The organ of Bojanus was not distinctly recognized. The gills are of a very 
primitive type, resembling the palpi of some Acephala in form, though not in 
construction ; there are no true palpi; the gills originate above the mouth 
and behind the anterior adductor ; their bases extend backward in a nearly 
right line to the lower surface of the posterior adductors, behind which two 
strong bands, one to each gill, anchor the main stem of the gill to the thick- 
ened margin of the mantle above and behind the adductors ; beyond the point 
where these muscular bands are attached, the bases of the gills curve downward, 
hanging free, and terminate in a point reaching to the lower posterior edge of 
the mantle. The aforesaid bases are broad stout bands carrying each a large 
vessel and sustained by a rather stiff (chitinous) framework, or fundamental 
tissue. From them proceed the gill-filaments, each of which is extremely long, 
* Like the acorn without its cup. 
