A. Gray on a new genus of Verbenacee. 97 
The erystals of sphene from northern New York, called Led- 
erite by Shepard, present actually the fundamental form here 
adopted, with simply a plane on each basal edge (2 or n and 
-% or t), and a truncating plane (i or P) on the front lateral edge. 
The inclination of the vertical axis is 119° 33’; and making a 
the vertical axisand 6 the clinodiagonal, a:b:e=0:4277:0-75414:1, 
The interfacial angle I: J (7 :r)= 113° 28’, O: li(y: x)= 158° 55’, 
L:1(2)=149° 38, 2:2(n)=136° 4. 
This mode of viewing the crystallization of sphene brings to 
light an approximate isomorphism of the mineral with Euclase. 
In euclase J: [=114° 50’, O:1i=158° 10, 1:1=1519 48’. The 
principal difference in the dimensions of the two is found in the 
greater length and inclination of the vertical axis in sphene, this 
inclination being in euclase but 108° 53’. Euclase has also a 
perfect clinodiagonal cleavage. 
In chemical composition, the species are widely different, 
sphene being a titano-silicate of lime (20a 8i+¢aTi*), and euclase 
a silicate of alumina and glucina (413+ Bet) Sit. 
Arr. XV.—Characters of Terraciza, a new genus of Verbena- 
cee; by Asa Gray, M.D. 
Tue plant which forms the subject of this article first came to 
my notice in the Texano-New Mexican collection made by the 
indefatigable Mr. Charles Wright, in the year 1849. In the same 
or the preceding year, it was likewise collected by the late Dr. J. 
Gregg, in the Northern part of Mexico. Fine specimens also 
were gathered by Mr. Wright on his second journey, while at- 
tached to the scientific corps of the Boundary Commission. In 
1851, while under the command of Col. Graham, he collected it 
on the northern border of the Mexican state of Sonora; in 1852, 
while returning under the orders of Major Emory, he again met 
with it in the western part of Texas. I presume it has likewise 
been found by Dr. C. C. Parry, and Dr. J. M. Bigelow, during 
the survey of the Rio Grande from El Paso downwards; but 
have seen no specimens from them. _ Specimens are in both of 
Mr. Wright’s distributed collections. I have, moreover, just de- 
tected it in the late Dr. Coulter’s Mexican collection, whose name, 
as being the first discoverer, the species may appropriately bear. 
The natural order to which the plant in question belongs is not 
very evident at first view. In Mr. Wright’s notes, made at the 
time of gathering it, the plant is mentioned as a doubtful Borra- 
ginacea ;—a view suggested by the deeply four-lobed fruit, and 
the nearly regular, pentamerous calyx and corolla. But the leaves 
Srconp Series, Vol. XVI, No. 46.—July, 1853. <a 
