Review of Recent Geological Literature. 381 
The author has followed the various authorities in naming the strati- 
graphic groups to which the species are assigned. Hence appear some 
incongruities, since palaeontologists have not been agreed as to what 
names should be used for the horizons to which their fossils belonged. 
Under the guide of palaaontologic distinctions these anomalies can 
nearly all be eliminated now, and various zones can be defined having 
common characters, embracing several of the old names in one zone. 
The questions of nomenclature for these zones are complicated and vex- 
atious ; but it seems to become more and more appropriate that the rule 
of priority should be as binding in geologic stratigraphy as in zoology. 
With that as a guide many synonyms which now are in conflict and an- 
noy the systematist, will drop out of the science. 
Note. Recent investigation in Palaeozoic Crustacea have added to the number 
of genera as follows: 
Cambric— Entomis 1, Pontocypris (?) 1, Ctenobolbina fa. g.) 6, Tetradella(n.g.) 6, 
Bollia 2, Drepanella (n. g.) 5, Jonesecla (n. g.) 4, Placentula 2, Beyrichia l, Eury- 
chilina 7, Primitia 11, Aparchites 1, Leperditia 4, Leochilina G. Total 57. 
Siluric— Entomis 1, Ctenobolbina 1, Aechmina 1, Octonaria 1, Bytliocypris 1. 
Total 5. 
Devonic— Cytherella 1, Ctenobolbina 4, Bollia 2, Beyrichia 3, Aparchites 1, 
Leperditia 1, Aechmina l, Halliella (n. g.) 1, Moorea 1, Kirkbya 3, Octonaria 5, 
Bytliocypris 2, Bairdia 1, Paehydomella (n. g.) l, Barychilina (n. g.) 3. Total 30. 
Carbonic— Pliillipsia 1, Pontocypris 1, Bollia 1, Beyrichia 2, Primitia 5, Leperdi- 
tia 1, Moorea l, Kirkbya 5, Bairdia l, Ulrichia 2, Cypridina l, Cytherella 2, Total 
23. Trilobites, 81 genera, 683 species. Palaeozoic Crustacea, 72 genera, 389 species. 
Trionyx from Malta. In the Quart. Jour. Geol. Soc. Feb. 1891, Mr. 
Lydekker describes a new species of Trionyx (T. melitensis) from the 
Miocene of Malta. The species is represented by a portion of the carap- 
ace, which, as restored, is about twelve and one half inches long and 
about twenty inches across. The species closely resembles Chitra 
indica and the author is only prevented from placing it under this genus 
by the fact there is no known instance in Chitra of a divided first neural. 
Palceosyops and Allied Genera, by Charles Eaei.e. (Proc. Acad. 
Natl. Sci. 1891, pp. 106-117.) This paper represents a considerable more 
comparison of the different species than has ever before been attempted; 
from this standpoint the paper is particularly valuable, if from no 
other. The author takes the trouble (?) to say that he has been able to 
compare the different specimens in the museums at Washington, Phila- 
delphia, Princeton, and New Haven, in which he is most fortunate, as 
Palceosyops has been in a most mixed-up state ever since it was first de- 
scribed. The Princeton specimen of P. jwludosus Leidy is made the 
basis of operations and, as the reviewer of this paper has said on former 
occasions, the work from the Princeton museum has been most satisfac- 
torily done. Mr. Earle thinks Leidy's P. major is synonymous with 
P. paludosus Leidy; the specimens representing the former equalling in 
every particular the original specimens of the latter and hence he sup- 
presses the species P. major. He has found two different individuals 
indicated as P. paludosus Leidy; to the smaller he applies the name P. 
minor, which no doubt equals some of Leidy's later P. paludosus but not 
the original. Cope's P. Icevidens is dropped, as not appropriate. The 
