254 MOLLUSCA. 
Cylindrella, but not in Holospira and Macroceramus, a number of the upper whorls are 
progressively lost during life, so that the individual has never at the same time the full 
number of whorls. The loss of the whorls during life is proved by the closing of the 
hole by a shelly, often slightly convex, wall (see Tab. XVI. fig. 28 a), whereas in worn 
dead shells, which by external injury have lost a part of the whorls, the hole of the 
fracture remains open. 
EUCALODIUM. 
Urocoptis, sect. a. Conico-turrite, Albers, Die Helic. ed. 2, p. 36 (1860). 
Eucalodium, Crosse & Fischer, Journ. de Conch. xvi. pp. 88 &c. (1868); Miss. Scient. Mex., 
Mollusca, i. pp. 353-362; Strebel, Beitr. Mex. Land- und Siissw.-Conch. iv. p. 62. 
Shell turrite, with many whorls, the uppermost always lost in the adult shell and 
the hole closed by a newly formed wall; last whorl somewhat narrowed and a little 
produced beyond the suture with the penultimate whorl; aperture roundish, with the 
edge free all round and a little expanded. Columellar axis solid (instead of hollow, as 
in Celocentrum), a little plaited. Surface covered by a distinct periostracum of pink, 
brownish, or yellowish colour and costulate in a somewhat oblique direction, these 
coste and markings, when present, being parallel with the edges of the aperture 
and more or less numerous, but never very prominent. Size comparatively large, 
between 84 and 32 millim. in length and 21 and 10 millim. in diameter. Number of 
remaining whorls 7-14, exceptionally more or less. Jaw arcuated, with feeble ribs. 
Teeth of the radula moderately pointed; median tooth a little smaller than the next 
ones, with a basal point on each side; lateral teeth with a basal point only on the 
outer side. Reproductive organs simple. For further anatomical characters, see the 
works of Fischer and Strebel. 
Geographically limited to the southern half of Mexico and the northern half of 
Guatemala: on the Atlantic slope, known from the neighbourhood of Misantla to the 
valley of the Polochic river, south of Coban; on the Pacific slope, only from Colima to 
Tehuantepec; rare in the central regions. The most characteristic and largest species 
on the Atlantic slope, those of the Pacific slope nearly all belonging to the subdivision 
Anisospira. ‘They live chiefly on the ground, in moist woods, or under leaves, such as 
those of Agave. 
The species are difficult to distinguish, as the outline of the shell sometimes shows 
individual variation. The absolute length of adult specimens is not a reliable character, 
as it varies much according to the number of preserved whorls; the diameter of the 
shell (measured on the whorl before the last) and the size of the aperture are, however, 
safer guides. The sculpture affords some specific differences, but the transverse or 
spiral striz, which are characteristic of several species, sometimes become very feeble 
or scarcely visible in certain individuals; in worn specimens it may be much altered. 
In some cases the amount of convexity of the single whorls, and the relation of the 
