GASTEROPODA. 149 
Cerithium celatum (Couthouy MS.), Goutp; Proceed. Boston Soc. 
Nat. Hist., iii. 123. May 1849. Expedition Shells, 62. 
ANIMAL small, yellowish flesh-colour, ochreous above, speckled 
with black dots; head short, mouth with a short, vertically com- 
pressed proboscis; tentacles subulate, a little compressed vertically ; 
eyes lateral, near the tips, without pedicles; locomotive disk elongated 
oval, truncate in front, the angles not dilated, with a longitudinal 
groove on the median line. Operculum oval, thin, semitransparent, 
yellow, unispiral, apex subterminal. 
SHELL subulate, or elongated-conical; colour purplish-brown ; 
whorls thirteen or fourteen, deeply impressed with broad, longitudinal 
sulci, with intervening folds of the same width, and decussated by 
two fine revolving lines, deeply indented as they cross the sulci, thus 
cutting each whorl into three bands of gemmules. 
On the base of the last whorl are only incremental lines. The 
suture is very deeply impressed, and has a delicate callus behind it, 
and the base is surrounded by two impressed strie, the marginal one 
strongest. Aperture nearly circular; columella strongly arcuated ; lip 
acute; canal short, inclining abruptly to the left and slightly ascen- 
dant. [3. P.c.] 
Length three-fourths of an inch; breadth one-fifth of an inch. 
Obtained at Orange Harbour, Tierra del Fuego. Couthouy. 
This species belongs to the same group as C. turritella, which it 
resembles; but in its delicate form it still more strongly resembles 
C. sardoum, Cantr. 
Figure 174, shell, with the animal, as in motion, enlarged; 174 a, 
174 6, front and basal view of the animal, enlarged; 174c, the shell, 
natural size; 174d, operculum, enlarged. 
CERITHIUM FILOsUM (Gould). 
Testa parva, elongato-turrita: spira anfractibus ad octo planulatis, 
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