TruEMAN.—-A New Fossil Gasteropod from New Zealand. 603 
ultimately disappear completely, sixth whorl being ornamented only by 
spiral lines and oblique growth-lines. On this whorl the spirals are very 
numerous, those near sutures being somewhat stronger than those 
on middle of whorl. It.may be suggested that this corresponds with the 
earliest whorl shown imperfectly in holotype. 
e ontogeny of K. obliquestriata may therefore be summarized as 
follow 
cue NER ? Whorl-shape. 
Protoconch .. Unkno .. Unknown. 
? Third whorl .. Axial со ete and s spira als .. Round. 
Fourth whorl ..  Feebler costae and spirals .. Round. 
Fifth whorl .. Spirals and subcostae .. Round. 
Sixth whorl .. Growth-lines and spirals . Flatter. 
Seventh to ténth apt uia lines and spirals near 
rl Flat 
who 
Eleventh whorl .. асса Е ‘and spirals near 
sutures es ка .. More tumid ; whorls 
embracing. 
Variations.—As remarked, there is considerable variation among the 
specimens, even in one piece of matrix. This is chiefly due to the accelera- 
tion or retardation of those progressive acorde that are summarized in 
the above table. us in some specimens the whorl-shape at any given 
stage is more or less advanced than indicated in the table. As the accele- 
ration of ornament takes place independently of the changes in mem 
shape, a t number of variants may be recognized. In some specim 
the whorls remain flat eru кану and there appears to be no adeny 
for the whorls to be moulded on the preceding ones; in other specimens 
this м. is attained by the iri: or seventh whorl. 
riation in acceleration of ornamentation is equally distinct. For 
. € illustrates the early whorls of a specimen in which the costate 
stage is ' lost by the fourth whorl; in several specimens the stage with 
spirals is retained until the seventh or eighth whorl. 
These differences are in several cases so e as to suggest that 
more than one species is present. Indeed, at one stage in the aserat 
tion, before the more complete material had been received, the writer was 
dis to refer the fragments to at least two species of different. genera. 
As they occur together, petes and as the variation in each character 
appears to be continuous, it is more satisfactory to regard them as members 
of one gens or species-group. The writer believes that members of the same 
species-group collected at one horizon not infrequently show such differences, 
due to differential acceleration of progressive characters. Such differences 
in isochronous members of one "lineage" have been noted in several 
divisions of the Mollusca 
a may be admitted that there is a possibility that m operis dealt . 
are not strictly isochronous; the limestone may in fossils of 
shy different dates; but, as the specimens are identical i in а 
appearance, it is safer to consider them as contemporaneous until 
par et to the contrary is tcs 
Generic Position.—Mesozoic' turriculate gasteropods with атаа 
axial ornament were formerly placed in Chemnitzia or in Pseudomelani 
Ps ia is taken to include smooth shells with growth-lines изиң 
straight, while smooth or costate shells in which the axials showed а 
sinuosity were placed in Chemnitzia 
* The more prominent feature in the ornamentation is given first in each сазе, 
