Geology and Mineralogy. 159 



by J. M. Clarke. From Rept. State Geologist K Y. for 1890, 

 pp. 13, 3 pi.; 7, 1 pi.; 6, 1 pi. 1891. — These critical observations 

 on Acidaspis, Coronura, and Terataspis, give important supple- 

 mental information to the previous knowledge of these forms. 

 Ceratocephala, a name proposed by Warder in 1838, was the first 

 distinctive term applied to any member of the well-defined group 

 currently known as Acidaspis, and is taken as the leading genus. 

 The author arranges the species in the following subgeneric 

 groups: Odontopleura Emmrich, 1839, Acidaspis Murchison, 

 1839, Ceratocephala Warder, sensu stricto, 1838, Dicranurus 

 Conrad, 1841, Selenopeltis Corda, 1847, A ncyropyge Clarke, 1891. 



The fortunate discovery of an entire specimen of Coronura aspec- 

 tans Conrad (sp.), terminates a long series of synonymical uncer- 

 tainties. It gives a remarkable confirmation to the conclusion 

 reached in vol. vii, Pal. N. Y., based upon fragmentary evidence, 

 that the eye described by Conrad and the pygidia described by 

 Hall and Meek belong to a single species. The author, more- 

 over, considers this as included in an earlier name, the Asaphus 

 diurus Green. 



The restoration of a specimen of Terataspis grandis Hall, based 

 on a large cephalon and on comparisons with other portions, gives 

 a length of twenty inches. It consequently represents the largest 

 individual trilobite known. The species had a highly differen- 

 tiated defensive armor, which with its great size made it one of 

 the dominant Paleozoic invertebrates. c. e. b. 



7. Cretaceous fossils of Syria. — R. P. Whitfield describes and 

 figures a number of Syrian species in the Bulletin of the American 

 Museum of Natural History for December, 1891. 



8. Annual Report of the Geologiccd Survey of Arkansas for 

 1890. Vol. II, The Igneous Mocks of Arkansas, by J. Francis 

 Williams, 457 pp., 8vo, 1891. John C. Branner, State Geolo- 

 gist. — This country affords no more interesting series of igneous 

 rocks than the elseolite-syenites and related rocks of Arkansas, 

 which Dr. Williams discusses w r ith admirable thoroughness in this 

 volume. It is at the same time a nearly new field, for though the 

 many rare and interesting minerals, particularly of the Magnet 

 Cove region, have been long known and often described, but little 

 has been published in regard to the nature and occurrence of the 

 rocks with which they are associated. Four regions are enumer- 

 ated, in which these, rocks occur: (1) that of Pulaski county or 

 Fourche Mountain ; (2) of Saline County ; (3) of Magnet Cove and 

 (4) the Potash Sulphur Springs. The Fourche Mountain rocks 

 which are largely used for building purposes, include the "blue 

 granite" here named pulaskite, a rock with trachytic structure 

 consisting of orthoclase, biotite, hornblende with but little augite, 

 elseolite, sodalite, etc.; also the "gray granite," or elajolice-syenite ; 

 further a variety of dike rocks ; there are also certain augitic rocks 

 to one of which — a kind of monchiquite (Rosenbusch) — the name 

 fourchite is given, while a sub-group under this is called ouachi- 



tite. The most varied and interesting; of the regions named is 



