332 Scientific Intelligence. 



Many important changes have been introduced among the 

 Strophomenoids and Productoids. Strophomena is restored to its 

 original type S.rugosa Raf. = Zeptcena planumbona Hall. This 

 leaves most of the species known as Strophomena, and typified 

 by S. alternately without a name. For this group the genus 

 Mafinesquina is proposed. Zeptcena rests on its original species 

 L. rhomboidalis Wilckens, sp. (== L. rugosa Dalman), and species 

 for many years passing as Leptcena sericea, L. transversalis, etc., 

 now fall under Plectambonites Pander, Streptorhynchns is re- 

 stricted to a species of the type of 8. pelargonatum, a Permian 

 fossil, and nearly all the species commonly known under this 

 designation from the Silurian and Devonian now come under the 

 genus Orthothetes of Fischer de Waldheim. In addition to 

 Mafinesquina, the following names are proposed for new generic 

 and subgeneric types among the Strophomenoids and Productoids: 

 Orthidium, Kayserella, Pholidostrophia, Jueptostrophia, Amphi- 

 strophia, Lep)tella, Christiania, Anoplia, Chonostrophia , and 

 Chonopectus. 



It will probably be found that Tropidoleptus and Vitidina 

 belong with the genera included in this volume. Oldhamina, 

 Lyttonia, and Richtofenia, also pertain to this portion. It is 

 hoped that a recognition of ordinal, subordinal, and patronymic 

 subdivisions will be accorded in the final work as an expression 

 of the views of the authors. Several anomalous inferences upon 

 related genera which have a structurally intermediate genus ap- 

 pearing at a later geological period could perhaps be better ex- 

 plained as morphological equivalents. In other cases geratology 

 is evidently an important factor. 



Any just criticism of this work would deal chiefly with a few 

 details of observations, minor differences of opinion, and trivial 

 points of generic relationships, and would in no way impair its 

 general usefulness. It must therefore stand as of the highest 

 authority on the genera of Palaeozoic Brachiopoda. c. e. b. 



3. Report of the Arkansas Geologiccd Survey for 1890, 

 John C. Branner, State Geologist. Vol. Ill, Whetstones and 

 JVovactdites of Arkansas, by L. S. Griswold. 444 pp. 8vo, 

 with colored geological maps and other illustrations. — Mr. Gris- 

 wold's report has great value, alike historical, practical and 

 scientific. The origin of the novaculite stratum, which in its 

 pure form is 99^ per cent silica, is referred to simple sedimenta- 

 tion, like that of an ordinary sandstone; it is a very fine siliceous 

 sand-deposit, somewhat calcareous, from which the minute cal- 

 careous grains have been leached out, so as to render the rock 

 porous. Only small portions of the stratum have the fineness of 

 texture fitted for the best whetstones. The stratum is of the age 

 of the lower part of the Trenton, as proved by the author through 

 the discovery of Graptolites, and has a thickness of about 1200 

 feet. It is underlaid by 1300 feet of shales, limestones and sand- 

 stones of older Paleozoic, and overlaid directly by 1200 to 1500 

 feet of Subcarboniferous beds, the Upper Silurian and Devonian 



