402 BULLETIN OF THE 



inner one. At the base of this free angle is a small swelling of the cutis, and 

 just inside of it toward the median line is a small elevated hemispherical 

 organ which appears to be an osphradium, or of a sensory nature. In the speci- 

 men (6) as preserved there are four branchial leaves in the length of a milli- 

 meter; the double series is about 45.0 mm. long (in specimen a, 81.5 mm.), so 

 that each gill (in specimen b) contains about 360 single leaflets, which indi- 

 vidually average about 3.5 mm. long, and 1.2 mm. wide at the base. The 

 free part of the gill extends about eight millimeters. 



The cavity of the mouth is large, and, as far as could be judged in the rotten 

 state of the parts, a large thin-walled crop had position immediately behind it. 

 The termination of the intestine was preserved; it forms a sigmoid curve on 

 the surface of the mantle behind the anal commissure, where it is (specimen b) 

 somewhat over 2.0 mm. in diameter, and gradually tapers to a stoutish point. 

 The last seven or eight millimeters of its length are free, and when living it 

 can doubtless be protruded outside the shell through the slit, for the discharge 

 of fasces. 



Immediately underneath this part of the intestine and spreading on each 

 side, lobed in a shape roughly trifoliate, is a large gland or pair of glands meet- 

 ing in the median line, and having a radiately rugose and irregular surface, in 

 which the depressions look not unlike little oblong pits. Within and close to 

 the mantle edge, one on each side of the commissure, is an oblong elevation 

 containing an oblique opening, apparently the openings to these glands, which 

 I suppose to have a renal function. 



The operculum is very much larger absolutely and proportionally than in 

 P. Quoyana. It measures (from the larger specimen) 54.0 mm. in maximum 

 and 47.0 mm. in minimum diameter, is almost flat, and has about ten whorls, 

 of which the central ones are rather indistinct. The outer surface is minutely 

 sharply spirally striated, and a central spot the size of a pin-head is indistinctly 

 indented. The inner side is polished, and shows a somewhat egg-shaped scar 

 of attachment. It is of an amber-brown color. The extreme margin is thin 

 and a little frayed. 



The jaws (specimen b) are situated in the same place, and are of about the 

 same form as in P. Quoyana, in fact are hardly larger than in that species, 

 although the P. Adansoniana is so much larger than the former. They are, 

 however, a little thicker and of a dark red-amber color. 



The radula is about 40.0 mm. long by 7.0 mm. wide in its natural condition 

 (specimen 6). As the characteristic teeth are figured, it is not necessary to 

 attempt a minute description in detail of each one. 



The rhachidian or central tooth is pointed before and Denind, or lozenge- 

 shaped, with a median rib, and the point or cusp hardly curved over at all. 

 It has sonfewhat the shape of a spear-head without barbs. The inner laterals 

 have somewhat the shape of a scapula, being oval, marginate, with a median 

 ridge from which a sort of recurved wing projects, near the base. There are 

 fifteen laterals on each side of the median line, gradually becoming more simple 

 in form as one follows the line outward ; then, of the uncini, the first five are 



