Review of Recent Geological Literature. 385 
as a mere verbal substitute for Nucida (Lam., 1799), as Dr. W. H. 
Dall and others have shown. Link's diagnosis applies to Xiicula 
and not to L'eda for he says that the shell is "smooth, closed all 
round." Nuculana (Link tion Adams) is therefore "an exact syno- 
nym" of Niicula and cannot be sustained on the ground of priority. 
Consequently the family name Niiai/ciiiida', Adams, cannot be re- 
tained for Ledidcc. c. e. b. 
Vestdftafaltet : En Petrogenetisk Studie. (With an English Summa- 
ry.) Af Helge Backstrom. (127 pp., 8 pis. Kongl. Svenska ^'eten- 
skaps-Akadamiens Handlingar, Bandet 2q, No. 4, 1897.) 
The crystalline schists of the Vestana region, which lies in north- 
eastern Scania, southern Sweden, have been studied and mapped in 
detail by Baron De Geer of the Geological Survey of Sweden. 
According to De Geer, they form an uninterrupted series of strata, 
striking northwest to northeast and dipping steeply to the west. 
From the youngest downward the sequence is as follows: 
C Fine-grained «iv.v fjiiciss. 
Klagstorp .schi,-ts -I 
f Diurj te-scliist. 
I Fine-grained, commonly red gneiss 
Dyneboda gneiss -1 
( witli layers of tlioryte-schist. 
r Mica-schist. 
I Quartzyte. 
Mica quartzyte -! 
I Mica-scbist ikHK coiu/lomerafe. 
I, Quartzyte with iron ore. 
r Black, hornblende-bearing, dense 
I flne-grained gneiss. 
Dense fine-grained gneiss.... -\ 
I Grey dense flne-grained gncdss. 
L Grey gneiss, less fine-grained. 
These gneisses and schists form a part of the Swedish Archaean 
(Lower Algonkian) and have been the subject of an able and pains- 
taking investigation, from a petrogenetic point of view, by Dr. 
Backstrom. 
Younger than the gneisses or crystalline schists there occur in the 
Vestana region numerous intrusive granite massives. Of these 
granites there is a prevalent fine-grained type ("Halen"-granite) and 
a less prevalent coarse-grained type ("Semshog" granite). These two 
types are closely related mineralogically and structurally. Both are 
characterized by scarceness of the ferromagnesian minerals and the 
predominance of microcline and quartz over oligoclase; hornblende 
is altogether absent; only biotite occurs; allanite and titanite are 
constant and often macroscopic constituents. Large microcline 
crystals are a characteristic feature of both granites, and give to 
them a porphyritic habit. This structure is called by Dr. Bacivstrom 
pseudoporphyritic, because the microcline does not belong to a first 
generation of crystallization, but, on the contrary, is younger than 
