518 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
.smaller, more .slender, and less shouldered and flaring at the aperture. 
That the female has to carry the material for the enormous ovicapsular 
mass is a sufficient reason for this difference in form and probabl}^ for 
the difference in size. Apart from this, many of the species have 
mutations of the coarser sculpture, which result in very unlike indi- 
viduals. They may be (1) rotund without strong keels or ribs, a state 
which I have called the normal form; (2) with strong spiral keels; 
(3) with strong axial ribs but no keels; (4) with both ribs and keels. 
I have enlarged on this subject elsewhere,^ and will not repeat the 
discussion here, but I may note that the males are relatively few in 
number, and it has been noted by Morse that they hide in rocky 
crevices too small to be entered by the females. At a time when the 
latter are on the sand beaches ovipositing the collector would probably 
find no males with them at all. 
On Plate XXXVII will be found illustrated several of the forms 
referred to. Fig. 3 represents Gray's angulosum., a female which is 
the form named stimpsoiii by Gould, strongly keeled and ribbed. 
Fig. 6, variety normale Dall, without keels or ribs, a male specimen. 
Fig. 2 represents a male of the type which carries ribs but no keels, 
and which in the Point Barrow report I called variety subcostatuvi. 
This specimen is not quite mature and has not formed the reflected 
lip. Lastly, fig. 1 represents a female specimen which has a distinct 
keel, but only faint wrinkles in place of ribs. In like manner fig. 7 
represents the normal form of Buccinum castaneum Dall, and tig. 9 
the carinate form, both being females. The latter when young has 
an astonishing resemblance to a young Chrysodomus liratus. 
In some species I suspect the discrepancy between the sexes is less 
noticeable, but in a keg of some 200 B. hydrophanum Hancock, from 
Baffin Bay, there were only nine males, all dwarfish. 
BUCCINUM PERCRASSUM Dall. 
Plate XXXVII, %. 4. 
Bucdnum {polare var. ?) percrassum Dall in Mart. u. Chemn. Conch. Cab. neue 
ausg., Buccinum (Kobelt), 1883, p. 86, pi. xci, fig. 5 (not of Posselt, 1898). 
Buccinum percrassum Dall, Proc. U. S. Nat. Mus., 1886, p. 216. 
Bering Island, Bering Sea, Grebnitzki. U.S.N.M., 108997. 
This remarkably solid species has an exceptionally large lozenge- 
shaped operculum. The specimen figured by Kobelt was of the type 
with small keels and riblets; that now figured is the normal form. 
The minute sculpture is quite distinct from that of B. oc/wtense Mid- 
dendorff' {B. i<chrciichu Verkruzen), which is also a rather solid species. 
It is nearest related to B. polare Gray, but I have not found yet any 
intermediate specimens. 
1 Nachric'htsblatt d. d. Malak. Ges., 1882. pp. 118-121. 
