MOLLUSCA FROM JUAN FERNANDEZ AND EASTER ISLAND 239 
Neanic shell (fig. 46) with a more pronounced columellar fold and a trace 
of a parietal Jamella. 
Localities: Masatierra, Aug. 1917: Rabanal, about 300 m above sea, I 
gerontic empty shell (type, fig. 45). — Puerto Ingles, about 400 m, thick forest, 
2 neanic small shells (fig. 46). 
From 7. ca/losa the present species differs in its wider aperture and stouter 
shape, in the absence of a columellar callus and the thinness of the columellar 
fold, as well as in having, in neanic stage, a feeble parietal lamella. The 
gerontic stage thus is very like the genus /ernandezia, which, however, is 
destitute of every armature in the aperture, even in young stages. 
General Remarks on Tornatellina, 
T. bilamellata and 7. conica have a common character in the persistent 
armature of the aperture, this being complete in all stages of growth, though 
subject to some variation especially in the first-named species. In the three 
other species described here as new, a difference between young (neanic) and 
old (gerontic) stages is to be observed, inasmuch as there are lamellae on the 
walls only in young sbells; the ephebic or mature stage seems to be like the 
neanic one in 7. flicosa, but in 7. cal/osa it is similar to the gerontic, which 
retains the columellar fold only. A reduction of the lamellation thus takes place 
in the last-named species, about the time of breeding, when the lamellae begin 
to be resorbed. An analogous reduction was stated in Pacificella variabilts, 
though in that species the columellar fold is the subject of resorption; other 
genera, too, such as Lamellina and Tornatellides, not to speak of certain 
Pupillidae, such as Laurza and Orcula, share this peculiarity, which, according 
to PILSBRY, is an indication of a great geological age. 
Only the last whorl is, however, in all species, furnished with lamellae, 
none are found, except occasional traces, within the upper whorls. A continuous 
resorption of the lamellae thus takes place in all species, as growth passes on, 
and this reduction also befalls, to some extent, the inner partitions which are 
always thinner than the basal wall of even young shells. 
The resorption process may perhaps be a consequence of the viviparity 
of the majority of fam. Tornatellinidae. In oviparous genera such as Auriculella 
and Tornatellaria, there is a greater similarity between adult and juvenile 
shells as regards lamellation. 
Observations on Anatomy. 
Some specimens of 7. dz/amellata were examined by studying series of 
sections and by dissection; also a couple of 7. flicosa in a beginning ephebic 
stage were dissected. 
The external habitus is like that of Pacificella (see below): a well-developed 
right mantle lobe, with a long anal furrow is present. The pallial organs are 
also similar: the kidney is extremely long and narrow, occupying somewhat 
more than one whorl, and furnished, at its distal end, with a longitudinal fold. 
