Editorial Comment. 193 
It is plain that Dr. Newberry took the Gryphcm dilatata var. 
tucumcarii or more exactly the Gryphcea tucumcarii Marcou — 
for it is truly a species of the group of the Gryphcea dilatata type 
of the European Oxfordian— for a Gryphcea pitcheri, at least in 
several instances; for he may have referred other species also to 
<?. pitcheri, which are neither G. pitcheri, nor G. tucumcarii. 
Without seeing his specimens it is impossible to know what his 
<Trijphwa of New Mexico are. 
The object of Dr. Newberry in quoting so often the Gryphcm 
pitcheri in New Mexico, was perhaps to sustain his conclusion 
that the "Jurassic rocks do not occur on any part of the route 
followed by Mr. Marcou, and where he claims to have discovered 
them." {Explor. Exped. Sante Fe to Green river, p. 142.) 
Lately, November 18, 1888, the University of Texas School 
of Geology, has issued a "Circular No. 1," in which we read: 
*'The reaffirmation of the age of the Tucumcarii section along 
the northwest corner of Texas to be uppermost Jurassic, as 
originally described by Marcou." It seems that professor Robert 
T. Hill is the first geologist, since my exploration of the Tu- 
■cumcarii area, more than thirty-five years ago, who has gone 
over the ground where I first discovered and described the Ju- 
rassic system in North America; and I shall wait until he has 
published his observations there, before writing another paper 
on the Gryphcea tucumcarii., as a suite and complement to the 
present paper on the Gryphcea pitcheri. 
Cambridge, 6 December., 1888. 
EDITORIAL COMMENT. 
Rejoindkk to Dk. Lawsox. 
Attention is directed to an interesting communication in the 
present number of the Geologist from the able pen of Dr. 
Lawson. It is written in reply to some condensed criticisms of 
the theory of the eruptive nature and origin of the great 
Archaean masses of granitic and gneissic rocks occurring north- 
west of lake Superior. The criticisms were embodied in the in- 
ferences based by the writer on three months' field-study of 
Archajan rocks in that region, and were directed specifically to 
