384 TJic A/iicrican Geologist. June, isgs 
preserved Gasfropoda. Mr. Harris has thus been enabled to study 
the larval shells and the stages of growth with accuracy and pre- 
cision. In studies of phylogenies and in the systematic classification 
of the Gastropoda the results are important. The scaphopods and 
lamellibranchs are also included, but owing to meager material they 
have afiforded insufficient data for general conclusions. 
Some valuable suggestions are given governing the correlations of 
phylogeny with chronology. Thus, a genus that has survived from 
early Mcsozoic times, with but little modification in the later stages 
of its history, has had its day and settled down to a more or less 
fixed form. Such a genus is of little use for homotaxial purposes, 
though interesting phylogenetically. In the Tertiary the determina- 
tion of homotaxis can best be based upon families which originated 
in Jurassic or Cretaceous times and reached the Eocene with strong 
tendencies to variation; yet, at the same time, the members should be 
capable of wide and rapid dispersion. 
The general law is suggested that when the main features of 
ornament are foreshadowed in the early nepionic or brephic stage, 
and especially when they obtain even in the protoconch, that orna- 
ment may be regarded as of value in the determination of species. 
On the contrary, when the ornament does not make its appearance 
until the late neanic or adolescent stage, and, even in an elementary 
sense, is not completed until what may be regarded, by analogy, 
as the earl}' mature stage, that ornament merely characterizes the 
individual, and is only of negative use for the purposes of classifica- 
tion. 
As is well known, the size of the protoconch is variable, even in 
the offspring of a single individual, that difference being commonly 
attributed to carnivorous proclivities on the part of the larger speci- 
mens when in the embryonic stage. The author also notes that the 
size of the protoconch does not seem to have much influence in 
determining the size of the shell in the adult. The larger protoconch 
is not very often accompanied by the production of a larger adult 
shell than that which comes from a much smaller protoconch, that is, 
■ in the same species. There are, however, exceptions to this, and, cor- 
relatively, it may be noted that the shape of the protoconch occa- 
sionally determines the general shape of the shell. 
Further interesting observations are made on the development of 
the VolutidcE, the columellar plications in Mitra, and the recurrence 
of a type of ornamentation in a species of Cerithiuiii. All the genera 
are briefly described, and the type species is given. The notes on the 
species are preceded by a list of the synonymy and bibliographic 
references. 
Some changes in the nomenclature of the genera will not meet 
with general endorsement, although the principles adopted are, for 
the most part, those approved by the best authorities. Thus, the 
mxix^- Nucitlana (Link, 1807) is used instead of Lcda (Schum., 1817) 
on the ground of priority. Nuculana however was given by Link 
