Occasional Papers of the Museum of Zoology 59 
give the shell much the appearance of some species of Thy- 
sanophora. In the bleached specimen the epidermis is gone 
and the growth-lines appear quite regularly parallel, but, under 
a lens, the larger excrescences can be made out as compara- 
tively slight, local developments of the growth-wrinkles. My 
specimens appear to be slightly more flattened above the sub- 
angulate periphery than in those figured by Fischer and Crosse 
(1902). The largest specimen measures: altitude, 8.8 mm.; 
greater diameter, 200 (17.7 mm.) ; lesser diameter, 170 (14.9 
mm.). 
In the specimen that was almost adult the remains of the 
dried animal were found, and the jaw and radula were obtained. 
The jaw (fig. 10) is broadly arcuate, has a central superior 
angulation, and bears 11 low, broad, striate ribs. The cutting 
edge has a transparent border, which is apparently much thin- 
ner than the basal portion. 
The radular formula (fig. 8) is: 
I 7 26 2 
C—;L—; M —— + — jor 36~-1-36. 
Seo a anes eet! 
The central tooth is comparatively broader than in A. coac- 
tiliata, and is definitely tricuspid. The ectocone and entocone | 
are borne rather near the tip of the mesocone, but are on the 
same level or slightly above it. The first 7 laterals are also 
definitely tricuspid. Beyond this, the teeth become more elon- 
gate, and the entocone is often bifid. Beyond the twenty-eighth 
tooth, the ectocone also is often double. The outermost teeth 
seen are short, very variable, and multicuspid. There may 
be a denticle or so beyond the outermost tooth detected, as 
the outer portion of the basal membrane was lost, due to 
trouble in mounting. Nevertheless, the vestigial character of 
