1894,] Geology and Paleontology. 267 
demonstrate the existence of the antenne was a felt weakness. That 
weakness has now been finally removed, and my arguments have been 
fully confirmed by the finding that the Trilobites had antenne in prac- 
tically the same position as the anterior pair in the Apodide. 
“The Trilobites may, therefore, take a firm place at the root of the 
Crustacean system, with the existing Apus as their nearest ally.” 
Development of the Brachial Supports in Dielasma and 
Zygospira.—Some interesting results have been obtained by Messrs. 
Beecher and Schuchert in studying the development of the brachial 
supports of the Terebratellidz. Some of the latest are embodied in a 
paper published in the Proceeds. Biol. Soc. Washington, 1893, in which 
the authors show that the most primitive form of the loop in the An- 
cylobrachia is centronelloid and that therefore Centronella represents 
a larval or immature condition of the higher genera. For demonstra- 
tion the authors use the paleozoic species, Dielasma turgida and give 
drawings of six sections to show the development of the loop. 
It is also shown that in Zygospira recurvirostra the primitive arm 
support is a terebratuloid loop having a Centronella form, which under- 
goes several modifications before the growth of the spiral lamellæ, in 
so far resembling the development of Dielasma. The spirals then de- 
velop as two slender converging lamellæ, curving toward the ventral 
valve, originating from the outer pointed ends of the loop. When 
maturity is attained there are about three volutions in each spiral cone. 
Sectional drawings illustrate this series of changes. 
Zygospira is the earliest spire-bearing genus known, and from the 
study of the ontogeny and phylogeny of its species the authors con- 
clude that the Ancylobrachia are older and more primitive than the 
Helicopegmata. 
According to the authors these results throw doubt on a number of 
Lower and Upper Silurian species described as having recurved loops 
and previously referred to Macandrevia or Waldheimia. The facts 
indicate that Waldheimia mawii, described by Davidson, is the young 
of Davia navicula Sowerby. 
Geological News.—Mesozoic.—Inm a recent journey across the 
plateau of Shan-si, China, Mr. Obrucheff discovered some fossil plants 
in the middle parts of the series of deposits which cover in China, the 
carboniferous formation, and which Richthofen had described under 
the names of Meberkohlen-sandsteine or Plateau-sandsteine. These 
Plants indicate that the middle portions of this formation belong to 
the Mesozoic age, and are Triassic or Liassic. (Nature, Jan., 1894.) 
