﻿974 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  their 
  inner 
  faces, 
  not 
  making 
  the 
  nooses 
  peculiar 
  to 
  Athtkis 
  

   proper 
  ; 
  they 
  are 
  broad 
  and 
  blade-like, 
  narrowing 
  beyond 
  the 
  

   insertion 
  of 
  the 
  jugum 
  ; 
  the 
  jugum 
  is 
  situated 
  posteriorly 
  ; 
  the 
  ac- 
  

   cessory 
  lamellae 
  are 
  narrow 
  near 
  their 
  origin, 
  broaden 
  and 
  then 
  

   taper 
  again, 
  having 
  the 
  shape 
  of 
  a 
  sickle. 
  The 
  spiral 
  ribbon 
  

  

  Fig. 
  312.— 
  The 
  fimbriated 
  spirals 
  of 
  Cliothyris 
  pectinifera, 
  Sowerby 
  (sp.). 
  (Davidson.) 
  

  

  appears, 
  from 
  the 
  figures 
  given 
  by 
  Davidson 
  and 
  King, 
  to 
  be 
  

   pectinated 
  on 
  all 
  its 
  outer 
  edges, 
  but 
  it 
  has 
  not 
  been 
  shown 
  that 
  

   the 
  anterior 
  extremity 
  of 
  the 
  jugum 
  is 
  similarly 
  ornamented 
  

  

  (Type, 
  Cliothyris 
  pectinifera, 
  Sowerby 
  (sp.). 
  Lower 
  Carbon- 
  

   iferous 
  — 
  Permian.) 
  

  

  Subgenus 
  Actinoconchus, 
  McCoy. 
  1844. 
  

  

  Shells 
  characterized 
  by 
  the 
  extravagant 
  development 
  of 
  the 
  

   concentric 
  lamellar 
  expansion, 
  which 
  are 
  striated 
  radially 
  by 
  dis- 
  

   tant 
  sulci. 
  These 
  expansions 
  appear 
  to 
  be 
  actually 
  fine, 
  tubular 
  

   spines 
  connected 
  by, 
  or 
  imbedded 
  in 
  a 
  tenuous 
  calcareous 
  plate. 
  

   The 
  interior 
  of 
  the 
  pedicle-valve 
  bears 
  a 
  median 
  septum 
  which 
  

   traverses 
  the 
  pedicle-cavity 
  and 
  half 
  the 
  length 
  of 
  the 
  shell 
  ; 
  

   also 
  tvvo 
  strong 
  dental 
  plates 
  which 
  are 
  continued 
  forward, 
  

   slightly 
  diverging, 
  for 
  more 
  than 
  one 
  half 
  the 
  length 
  of 
  the 
  sep- 
  

   tum. 
  Mr. 
  Davidson 
  has 
  given 
  elaborate 
  illustrations 
  of 
  the 
  spirals 
  

   and 
  loop 
  of 
  this 
  species, 
  from 
  preparations 
  by 
  the 
  Eev. 
  Nokman 
  

   Glass, 
  and 
  from 
  them 
  it 
  appears 
  that 
  the 
  latter 
  organ, 
  the 
  

   jugum, 
  has 
  essentially 
  the 
  same 
  conformation 
  as 
  in 
  Cliothyris 
  

   pectinifera, 
  though 
  placed 
  further 
  forward. 
  The 
  saddle 
  of 
  the 
  

  

  32 
  

  

  