﻿Geology 
  and 
  Mineralogy. 
  477 
  

  

  petiolata 
  Goepp., 
  is 
  allied 
  to 
  the 
  A. 
  sphenophylloides 
  and 
  A. 
  

   macilenta 
  published 
  without 
  illustration 
  by 
  Lesquereux. 
  The 
  

   fructification 
  of 
  this 
  species 
  described 
  by 
  Schmalhausen 
  with 
  con- 
  

   siderable 
  detail, 
  resembles 
  that 
  of 
  A. 
  minor 
  Lx. 
  and 
  others, 
  but 
  

   the 
  sporangia 
  are 
  few. 
  Being 
  unable 
  to 
  find 
  satisfactory 
  family 
  

   connections 
  between 
  the 
  genus 
  Archceopteris 
  and 
  any 
  other 
  living 
  

   or 
  fossil 
  type 
  of 
  ferns, 
  the 
  author 
  proposes 
  the 
  group 
  Arcbaaop- 
  

   teridae. 
  It 
  is 
  not 
  unlikely 
  that 
  the 
  spiral 
  arrangement 
  of 
  the 
  

   leaves 
  in 
  the 
  Russian 
  species 
  noted 
  by 
  Schmalhausen 
  is 
  also 
  indi- 
  

   cated 
  in 
  our 
  American 
  species 
  of 
  Archceopteris 
  by 
  the 
  alternation 
  

   of 
  pinnules 
  with 
  pinnae 
  in 
  the 
  ramification. 
  

  

  The 
  Karakuba 
  flora 
  is 
  remarkable 
  in 
  having 
  more 
  fertile 
  than 
  

   sterile 
  species. 
  On 
  certain 
  clavate 
  or 
  bivalvate 
  " 
  capsules 
  " 
  

   strongly 
  resembling 
  the 
  fruit 
  of 
  Sphenopteris 
  Harveyi 
  Lx. 
  or 
  

   Zeilleria, 
  the 
  author 
  founds 
  the 
  new 
  genus 
  Dimeripter 
  is. 
  D. 
  grac- 
  

   ilis 
  and 
  D. 
  fasciculata 
  are 
  compared 
  by 
  Schmalhausen 
  with 
  

   Sphenopteris 
  Hitchcockiana 
  Dn. 
  and 
  S. 
  cojidrusorum 
  Gilk. 
  The 
  

   first 
  is 
  very 
  suggestive 
  of 
  the 
  fertile 
  S. 
  Harveyi 
  of 
  the 
  Potts- 
  

   ville 
  series 
  in 
  this 
  country, 
  while 
  the 
  other 
  reminds 
  one 
  at 
  first 
  

   glance 
  of 
  the 
  fruit 
  of 
  Calymmatotheca 
  bifida 
  (L. 
  and 
  H.) 
  Kidst. 
  

   from 
  the 
  Calciferous 
  sandstone 
  series 
  of 
  Scotland. 
  The 
  author 
  

   ■compares 
  his 
  Lepidodendron 
  Karahubense 
  with 
  L. 
  Gaspianum 
  

   Dn. 
  and 
  L. 
  nothum 
  Ung. 
  The 
  flora 
  as 
  a 
  whole 
  is 
  considered 
  as 
  

   indicating 
  an 
  Upper 
  Devonian 
  age. 
  d. 
  w. 
  

  

  7. 
  Contributions 
  a 
  VEtude 
  des 
  Feldspaths 
  des 
  Roches 
  Vbl- 
  

   caniques 
  par 
  F. 
  Fouque. 
  8vo, 
  pp. 
  336. 
  Paris 
  (ImprimerieChaix) 
  

   1894. 
  — 
  This 
  excellent 
  work 
  is 
  another 
  token 
  of 
  the 
  manner 
  in 
  

   which 
  the 
  demands 
  of 
  petrography 
  have 
  in 
  recent 
  years 
  stimu- 
  

   lated 
  research 
  in 
  mineralogy 
  along 
  certain 
  lines. 
  Along 
  with 
  the 
  

   work 
  of 
  Michel 
  Levy, 
  Federov, 
  and 
  Becke, 
  the 
  petrographer 
  

   has 
  now 
  placed 
  at 
  his 
  disposal 
  a 
  variety 
  of 
  means 
  by 
  which 
  the 
  

   problem 
  of 
  the 
  determination 
  of 
  the 
  feldspars 
  by 
  optical 
  methods 
  

   can 
  be 
  successfully 
  attacked. 
  

  

  The 
  volume 
  under 
  consideration 
  is 
  divided 
  into 
  four 
  parts. 
  

   In 
  the 
  first 
  the 
  author 
  points 
  out 
  the 
  methods 
  by 
  which 
  the 
  deter- 
  

   mination 
  of 
  the 
  feldspars, 
  especially 
  the 
  plagioclase 
  group 
  in 
  thin 
  

   sections, 
  may 
  be 
  resolved. 
  His 
  method 
  is 
  chiefly 
  by 
  the 
  measure- 
  

   ment 
  of 
  the 
  angle 
  of 
  extinction 
  with 
  the 
  edge 
  of 
  c(001) 
  on 
  6(010) 
  

   in 
  sections 
  perpendicular 
  to 
  bisectrices 
  ; 
  in 
  the 
  second 
  part 
  are 
  

   given 
  the 
  facts 
  obtained 
  from 
  a 
  chemical, 
  optical 
  and 
  crystallo- 
  

   graphic 
  study 
  of 
  a 
  large 
  number 
  of 
  species, 
  on 
  which 
  the 
  process 
  

   is 
  based. 
  In 
  the 
  third 
  portion 
  is 
  presented 
  the 
  petrographic 
  

   study 
  of 
  a 
  large 
  number 
  of 
  volcanic 
  rocks 
  chiefly 
  from 
  the 
  Haute 
  

   Auvergne 
  which 
  furnish 
  examples 
  of 
  the 
  author's 
  methods 
  and 
  

   contain 
  moreover 
  many 
  facts 
  of 
  petrographic 
  interest. 
  

  

  The 
  last 
  portion 
  contains 
  a 
  general 
  discussion 
  of 
  the 
  nature 
  of 
  

   the 
  soda-lime 
  feldspars 
  with 
  respect 
  to 
  their 
  chemical 
  constitution. 
  

   The 
  author 
  does 
  not 
  view 
  this 
  group 
  as 
  a 
  case 
  of 
  isomorphism 
  

   with 
  all 
  possible 
  mixtures 
  of 
  the 
  albite 
  and 
  anorthite 
  molecules, 
  

   but 
  from 
  the 
  frequency 
  of 
  certain 
  extinction-angles 
  and 
  other 
  

  

  