210 
POPULAR SCIENCE REVIEW. 
Square centimeter 
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Cubic millimeter . 
. cmm 
Square millimeter 
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t 
Cubic meter 
. cbm 
Kilogramm . 
• kg 
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No stops are to follow tlie letters. The letters are to he placed after the 
figures which express the amount, not over the decimal point: 5,37m, not 
5m, 37cm. In separating the integral numbers from those representing the 
decimal part a comma is to be employed in place of a full stop. The 
comma is not to be otherwise used when writing numbers representing 
measures of weight or capacity, not as formerly to divide high integral 
numbers ; in such cases the digits are to be divided into groups of three, 
counting from the comma (our decimal point), and the division between the 
groups is to be marked by a space. The new system has been introduced in 
the columns of the “ Ohemisches Central-Blatt.” (See note in u Chem. 
Central-Blatt,” January 2, 1878, xvi.) 
GEOLOGY AND PALAEONTOLOGY. 
An American Jurassic Ceratodus. — In the January number of u Silliman’s 
Journal ” Professor Marsh describes an interesting discovery he has made 
among the vertebrate fossils obtained from the same Upper Jurassic deposits 
of Colorado which furnished the gigantic Saurians noticed in our last number 
(p. 103). This is the left lower dental plate of a fish of the curious genus 
Ceratodus , which Professor Marsh names C. Giintheri in honour of Dr. Gun- 
ther of the British Museum. The specimen has the inner side convex and 
the outer divided into five projections, separated by four notches, the upper 
edge showing five points, of which the foremost is the longest and most 
widely separated. The plate is attached to a fragment of the dentary bone, 
and furnishes the first evidence of the existence of Ceratodus in America in 
Mesozoic times. 
Silurian Land Plants. — Professor Lesquereux has described (in the “ Proc. 
Amer. Phil. Soc.,” 19 Oct. 1877) and figured some terrestrial plants from 
the Lower Silurian. These are Protostigma sigillaroides from the Cincinnati 
group of Ohio ; and Psilophyton gracillimum and Sphenophyllum primcevum 
from the same rocks near Covington, Kentucky. 
A Carbonifei'ous Fungus. — In the above cited paper Professor Lesquereux 
also describes a fungus ( Rhizomorpha sigillarice) found upon a Sigillaria in 
Cannel coal at Cannelton, Kentucky. 
New American Dinosaurs. — Professor Marsh now forms a new family, 
Atlantosauridce , for the gigantic Jurassic Dinosaur noticed in our last number 
(p. 103), and indicates as its more important characters the pneumatic cavi- 
ties in the vertebrae, the presence of only three or four vertebrae in the 
sacrum and the corresponding shortness of the ilium, the large fore-limbs, 
and the presence of five well-developed digits in both fore and hind feet. 
The hind foot was ungulate and essentially plantigrade. The carpal and 
