Rev. N. Glass—The Spirals of the Brachiopoda. 79 
Hindella, belonging to the Anazygida, the primary lamellz shortly 
after attachment to the hinge-plate are bent backwards towards the 
ventral valve, each lamella forming an acute angle with the com- 
mencement of the first convolution of the spiral (this attachment 
was discovered by Davidson in 1858). In Nueleospira, Hall, and 
Athyris, M‘Coy (Glass, 1882), this angle is bent or curved under 
like a beak. In some American species of Athyris, M‘Coy (Whitfield, 
1859), the angle is not acute, but more open and loop-like. In 
Atrypide and Anazygide the primary lamelle shortly after attach- 
ment to the hinge-plate are bent outwards towards the lateral 
margins of the shell. 
Tue Loop, or THE CoNNECTIONS OF THE SPIRALS WITH EACH OTHER. 
In the Spiriferide the principal character is the straight attach- 
ment of the spirals to the hinge-plate. In Spirifera (Davidson, 1858) 
the loop is imperfect, consisting of two internal processes, arising 
from the primary lamellz, and directed downwards between the 
spirals, but not uniting. In Cyrtina, Dav. (Glass, 1882), these pro- 
cesses unite at an acute angle. In Spiriferina, D’Orb. (Davidson, 
1851), the loop consists of a straight or curved horizontal band 
almost on a level with the dorsal surface of the spirals. 
In the Atrypide the principal character is the position of the 
loop exterior to and above the spirals. The loop is directed down- 
wards, and is simple and rounded (Whitfield says that in some 
examples of Atrypa the loop is acutely angular—this had never 
been observed, however, by Dr. Davidson or myself). In Atrypa, 
M‘Coy (Whitfield, 1866), the loop is small, in Zygospira, Hall 
(Whitfield, 1862), it is much wider, and lower down, and curves 
upwards towards the hinge. 
In the Anazygide the principal character is the position of the 
loop rising from the bottom of the spirals. In Anazyga (Glass, 
1882) the loop is simple and rounded, and exterior to the spirals. 
In Hindella, Dav. (Glass, 1882), the loop is ‘simple and rounded, 
with a short spinous extremity, and interior to the spirals. In 
Dayia, Day. (Glass, 1880), the loop is simple and angular, with 
a short spinous extremity, and it is placed between the primary 
lamellee on the dorsal side of the spirals. 
In the Nucleospiride the principal character is the presence of a 
simple loop, more or less angular, between and near the centre of 
the spirals, and directed almost horizontally from the dorsal to the 
ventral side of the spirals—for example, Nucleospira, Hall (Whitfield, 
1859). 
In the Athyridg the principal character is the presence of an 
internal loop more complex than that of the Nucleospiride, and 
extending upwards from the centre of the spirals. The loop of the 
Athyrid@ is really an extension in an upward direction of the simple 
loop of the Nucleospiride. In Bifida, Dav. (Glass, 1882), there isa small 
bifurcation at the end of the simple loop. In Whitfieldia, Dav. (Glass, 
1881), the loop is extended further upwards than in Bifida by a 
rather long single process, which occurs between the simple loop 
