216 A. FE. Verrill— Mollusca of the New England Coast. 
faint, or entirely disappear, though a part of them sometimes continue 
to the anterior end, where they are distant and appear only as slightly 
indented furrows or depressions; at about the posterior third the 
number of grooves varies from twenty to forty. 
Color, usually grayish or slaty brown externally, bluish white 
within; more perfectly grown and younger specimens are white on 
the anterior portion and only faintly bluish white within, 
Length of an average specimen, 82™"; diameter, at the anterior 
end, 10™; at the posterior-end, 2". A more slender specimen is 
75" ™ long; diameter of the oral end, 9™"; of the posterior end 
la le 
This species was taken in considerable numbers at numerous sta- 
tions by the Albatross. Station 2050, im 1050 fathoms; 2052, in 1098 
fathoms; 2077, in 1255 fathoms, numerous specimens, living and 
dead (No. 34,904) ; 2083, in 959 fathoms, two specimens (No. 34,687) ; 
2084, in 1290 fathoms, numerous specimens, living and dead (No. 
24,911 and No. 34,688) ; 2102, in 1209 fathoms, one specimen; 2103, 
in 1091 fathoms, numerous living specimens (No. 35,636); 2104, in 
991 fathoms, two dead; and off Cape Hatteras, at station 2111, in 
938 fathoms, numerous living specimens (No. 35,635); 2115, in 843 
fathoms, one fine specimen (No. 35,645). 
This fine large species might readily be taken for a gigantic form 
of D. striolatum or D. occidentale. It is, however, a much stouter 
shell than either of these, of a thicker and firmer substance, and 
with a relatively larger aperture. It differs also in the character of 
the longtitudinal sculpture. In D. occidentale the longitudinal 
grooves are more numerous, broader and deeper, having more the 
character of true furrows, with the intervening ridges mostly nar- 
rower than the grooves, from which they rise rather abruptly, with 
well-defined border, while in the present form the grooves are merely 
depressions in the general surface of the shell, with indefinite borders. 
In D. striolatum the longitudinal sculpture is almost obsolete, ex- 
cept near the posterior end; and such lines as exist have the same 
character as in D. occidentale, though fainter, the two forms possibly 
being only varieties of one species. The most perfect specimens of 
D. solidum have also two posterior notches, while in D. striolatwn 
there is usually a single notch on the dorsal side, but the character 
of the posterior aperture seems to be variable in most of the species 
of this group. 
