Correspondence. 191 
gives rise seems to be in regarding it as an anorthite, not as an an- 
orthoclase rock. The name was properly given, the mineralogy of the 
rock was perfectly understood, the name properly indicated the miner- 
alogy, and was transferred to the group of igneous rocks of which the 
Canadian occurrences are the types when their igneous origin was 
recognized. It has come into large use as applied to a perfectly defi- 
nite rock group, and in my judgment both the requirements of priority 
and the dictates of common sense necessitate its continued use, rather 
than the injection of a substitute name into a literature which is already 
suffering indigestion from a surfeit of new names. 
The only objection urged against the name which has come under 
my notice and which seems to me to be valid has been urged by Kold- 
erup.* He argues that the name is equally applicable to an albite or 
oligoclase rock and that these are too acid to be grouped with rocks 
which are properly regarded as an end series of the gabbro family, 
This same objection would apply equally to plagioclasyte, recently 
proposed by A. N. Winchell to replace anorthosyte. But such rocks 
are of the rarest, so that the objection seems more theoretical than 
real. Kolderup proposes no substitute, but argues for the use of lab- 
radorfels, anorthitfels, etc., and does away with the group name. 
There can be no possible objection to this minuter subdivision where 
it is possible, but for the purpose of mapping, in the Adirondacks at 
least, it is not possible, and the more comprehensive name, or a more 
comprehensive name, is an absolute necessity. 
The Adirondack geologists have consistently followed the Canadian 
lead in the use of the term anorthosite, believing that no sufficient 
grounds exist for a substitute name, and are glad to take the lead in 
a protest against an attempt to shelve it. H. P. CUSHING. 
Above statement was submitted to Profs. Kemp and Smyth for their 
approval or disapproval, and their comments follow. 
I fully agree with the statements of Professor Cushing as given 
above. They are correct in fact and sound in principle. J. F. KEMP. 
Professor Cushing’s views in regard to the term anorthosite seem 
to me right, beyond question. Cc. A. SMYTH, JR. 
New York AcApeMy oF SCIENCES. JAN. 20. Professor R. P. Whit- 
field read two papers. The first was upon the Ammonite Heteroceras 
simplicostatum, in which he amended and elaborated the description of 
that species which he had given in the Newton and Jenny report on 
the Black hills, published in 1880, the new observations being based 
upon material gathered by Dr. E. O. Hovey on an expedition of the 
American Museum last summer. This material shows conclusively 
that the three genera Hamites, Ancyloceras and Heteroceras have no 
independent existence, because single individuals show the distinguish- 
ing characters of all three genera combined. This fact has been sus- 
pected by the author when at work upon the Newton material twenty- 
five years ogo, and it has been hinted at in writings of Hyatt ane 
*Bergens Museums Aarbog, 1896, Die labradorfelse, etc., p. 23. 
