C@LOCENTRUM. 267 
CGZLOCENTRUM. 
Eucalodium, sect. 2, Crosse & Fischer, Journ. de Conch. xviii. p. 22 (1868). 
Calocentrum, Crosse & Fischer, Journ. de Conch. xx. p. 802 (1870) ; Miss. Scient. Mex., Mollusca, 
1. p. 3389; Strebel, Beitr. Mex. Land- und Siissw.-Conch. iv. p. 56. 
Characterized by the hollow columellar axis, in other respects very near Hucalodium. 
The hollowness of the columella cannot be seen at the base of the adult shell, where 
it is reduced to a very small slit, or even closed, as in Eucalodium; but it is visible in 
all specimens on the upper truncate end of the shell, where it appears asa round 
exactly central hole. The outside of the columella is ordinarily sculptured by 
descending plaits or coste, but this can only be seen by breaking a hole into the shell. 
Moreover, the whorls are generally closer together than in Hucalodium, i.e. the height 
of the visible part of each whorl is less in relation to its diameter; the general outline 
is more fusiform—swollen in the middle, attenuated at both ends ; and the aperture is 
still smaller in comparison to the diameter. The colour in most of the species is 
brownish-yellow, without red or violet hue. Jaw smooth, with median projection. 
Teeth of the radula as in Eucalodium. 
The geographical distribution of Celocentrum is also similar to that of Hucalodium. 
With one exception, C. irregulare, Gabb, from Moleje in ‘‘ Mexican California,” all 
the known species are peculiar to Central America; but the northern limit, as well as 
the southern, slightly exceeds that of Eucalodium, the southernmost species being 
C. championi, from Cerro Zunil, on the Pacific slope of Guatemala. 
The species may be arranged for easier recognition into four subdivisions :— 
1. Shell large, subturrite, with feeble, somewhat irregular costz and distinct spiral striz between 
them : length 54-80 millim.—gigas, championi, clathratum, anomalum. 
2. Shell more swollen, spindle-shaped (fusiform), its greatest diameter not in the penultimate 
whorl, but higher upwards; coste feeble, close together: length 34-54 millim.—turvis, 
clava. tomacella. 
3. Shell small, more cylindrical, also with close feeble costa, dull coloured : length 20-30 millim. 
—arctispira, fistulare. 
4. Shell small, with comparatively strong coste, dark reddish-brown in colour: length 20-30 
millim.—crosseanum, filicosta. 
1. Celocentrum gigas, sp.n. (Tab. XVI. figg. 27, 28, 28 a, 4, ¢.) 
Shell measuring 21 millim. in diameter and 80 millim. in length (truncate), yellowish-grey, with numerous 
rather fine, somewhat arcuated costule, of which there are 98 on the whorl before the last, somewhat 
unequal and irregular, the interstices twice or thrice their breadth ; spiral strive in the interstices very 
feeble, none on the costule (fig. 286). Whorls a little convex, numbering 12 in the adult truncate 
example, about 24 in all, to judge from comparison with a young specimen; the height of the visible 
part of a whorl varying from # to 3 of its diameter, the middle whorls being not so high as the upper and 
the last seven whorls nearly equal in diameter, the preceding ones gradually diminishing 
upwards, so that the whole shell is turrite, but not properly fusiform. Base of the last whorl rounded, 
with a rather broad and shallow spiral furrow in the prolongation of the suture, instead of the usual 
angular line (fig. 28). The aperture, in the single, perhaps not quite perfect, adult specimen is scarcely 
34* 
lower ones ; 
