Reviews— Winchell & Schuchert—L. Silurian Brachiopoda. 423 
spiral loop are discussed. It begins life as a simple centronelloid and 
is characterized by subsequent progression from one to six whorls 
in each spiral. Beecher and Schuchert express the opinion that 
the ontogeny and phylogeny of Zygospira indicate the derivation 
of the Aérypidae from forms with a centronelloid loop, consequently 
“‘the Ancylobrachia are older and more primitive than the Helico- 
pegmata.” In asecondary communication published the same date? 
Mr. Charles Schuchert discusses the development of the shell in 
Zygospira recuvirostra, for which species Davidson proposed the 
genus Anazyga. The genus Zygospira was founded by Hall in 1860, 
with Producta modesta, Say, as type from the Hudson River group. 
The genus is remarkable for the extreme variability in the position 
of the loop in different individuals. This variation is individual, 
not specific, and therefore Hall and Clarke reject Davidson’s name 
Anazyga for the species recurvirostra of the genus Zygospira. Accord- 
ing to Schuchert, the fourth stage of shell development is reached 
before the species ‘“‘is recognizable as belonging to the sub- 
order Rostracea, and apparently most closely related to the Rhyn- 
chonellide. The calcareous brachial supports make their appearance 
in a specimen about 1:33 mm. in length. This species is then 
referable to the Ancylobrachia, having a loop much lke that of 
Centronella. This loop then passes through a series of metamor- 
phoses, acquiring spirals when the shell is about 3 mm. in length.” 
It would seem from a cursory glance through Hall and Clarke’s 
fascicle 1. part ii. vol. viii., Paleeozoic Brachiopoda, which has just 
reached us, that about ten new genera and sub-genera are proposed 
for the spire-bearing genera of Brachiopoda. 1. Many of them seem 
to be interesting passage forms of an inter-generic character. 
Messrs. N. H. Winchell and C. Schuchert have also described and 
ficured “Sponges, Graptolites and Corals” from the Lower Silurian 
of Minnesota, in chapter ili. with two plates, an excerpt from the 
same Report.? Herein the authors discuss the curious fossil sponges 
Receptaculitide, a family referred by that excellent authority, Dr. 
G. J. Hinde, to the siliceous Hexactinellid order. Their systematic 
position, however, has been regarded as doubtful by Nicholson, on 
the grounds of Rauff’s discovery that the original structure of the 
organism was calcareous, and it became silicified subsequently. 
Specimens of the genus Receptaculites occur from four to twelve 
inches in diameter in the Lower Silurian of Minnesota, where they 
are popularly known as the “sun-flower coral of the North-West.” 
The authors give a useful synopsis of the American species of the 
genera Receptaculites and Ischudites, followed by an essay on the 
structure of the anomalous organisms they formerly named anoma- 
loides, for which they now propose the correct and more suggestive 
name of Anomalospongia. They also give figures and descriptions 
of a species of hydroid Solenopora (S. compacta Billings), of species 
1 Development of the shell in Zygospira recurvirostra, By Charles Schuchert, 
Proc. Biol. Soc. Washington, vol. vili., pp. 71-82, pls. x., xi., July 13th, 1893. 
2 Final Report of the Minnesota Geological Survey, pp. 55-95, pls. F, G, 
June, 1893. 
