﻿998 
  JEORTY-SEVENTH 
  REPORT 
  ON 
  THE 
  STATE 
  MUSEUM. 
  

  

  ment. 
  No 
  trace 
  of 
  the 
  loop 
  has 
  been 
  found, 
  and 
  it 
  is 
  highly 
  

   improbable 
  that 
  a 
  species 
  agreeing 
  in 
  all 
  known 
  points 
  of 
  

   structure 
  with 
  the 
  spirigerous 
  groups 
  just 
  discussed 
  and 
  having 
  

   also 
  a 
  fibrous 
  shell 
  should 
  possess 
  such 
  a 
  structure. 
  

  

  (Type, 
  Leptocwlia 
  flabellites, 
  Conrad 
  (sp.). 
  Lower 
  Devonian 
  ; 
  

   New 
  York, 
  New 
  Brunswick, 
  Brazil, 
  Bolivia, 
  South 
  Africa). 
  

  

  Vitulina, 
  Hall. 
  1860. 
  

   (Plate 
  39, 
  figs. 
  28-36.) 
  

  

  Shell 
  of 
  rather 
  small 
  size 
  ; 
  plano-convex 
  in 
  contour, 
  transverse, 
  

   the 
  hingt-line 
  making 
  the 
  greatest 
  diameter 
  of 
  the 
  valves. 
  The 
  

   pedicle- 
  valve 
  is 
  convex, 
  its 
  umbo 
  scarcely 
  elevated 
  and 
  its 
  apex 
  

   not 
  prominent 
  or 
  incurved. 
  A 
  cardinal 
  area 
  is 
  highly 
  developed, 
  

   and 
  is 
  divided 
  medially 
  by 
  an 
  open, 
  triangular 
  delthyrium, 
  which 
  

   bears 
  no 
  traces 
  of 
  deltidial 
  plates 
  in 
  any 
  condition 
  that 
  has 
  been 
  

   observed. 
  The 
  delthyrium 
  is 
  very 
  wide, 
  its 
  base 
  covering 
  more 
  

   than 
  one-third 
  the 
  extent 
  of 
  the 
  hinge-line. 
  The 
  teeth 
  are 
  blunt, 
  

   thickened, 
  and 
  not 
  supported 
  by 
  dental 
  plates. 
  The 
  scar 
  of 
  the 
  

   pedicle-muscle 
  is 
  distinctly 
  defined, 
  but 
  those 
  of 
  the 
  other 
  mus- 
  

   cles 
  are 
  obscure 
  in 
  their 
  limitation. 
  Under 
  the 
  most 
  favorable 
  

   preservation, 
  there 
  appears 
  a 
  posterior 
  pair, 
  flabellate 
  in 
  form, 
  

   situated 
  just 
  in 
  front 
  of 
  the 
  pedicle-scar, 
  and, 
  more 
  anteriorly, 
  a 
  

   median 
  scar 
  enclosed 
  by 
  two 
  anterior 
  diductor 
  impressions. 
  

   There 
  is, 
  at 
  times, 
  a 
  low 
  median 
  ridge, 
  which 
  is 
  purely 
  muscular 
  

   in 
  its 
  origin. 
  

  

  The 
  brachial 
  valve 
  is 
  depressed-convex 
  or 
  flat 
  ; 
  it 
  bears 
  a 
  nar- 
  

   row 
  cardinal 
  area 
  coextensive 
  with 
  that 
  on 
  the 
  opposite 
  valve. 
  

   The 
  delthyrium 
  is 
  wide 
  and 
  open, 
  and 
  when 
  the 
  conjoii 
  ed 
  valves 
  

   are 
  viewed 
  from 
  behind, 
  the 
  cardinal 
  process 
  and 
  socket-walls 
  

   are 
  clearly 
  seen 
  through 
  the 
  wide 
  pedicle 
  passage. 
  The 
  former 
  

   of 
  these, 
  the 
  cardinal 
  process, 
  is 
  a 
  straight, 
  simple 
  apophysis, 
  

   like 
  that 
  in 
  Anoplotheca 
  and 
  Ccelospira 
  ; 
  and 
  the 
  socket 
  walls, 
  

   which 
  are 
  also 
  tiae 
  bases 
  of 
  the 
  crura, 
  are 
  short, 
  but 
  prominent 
  

   and 
  elevated, 
  bordering 
  deep 
  and 
  narrow 
  dental 
  sockets. 
  The 
  

   brachidium 
  consists 
  of 
  loosely 
  coiled 
  spirals 
  of 
  about 
  four 
  volu- 
  

   tions, 
  the 
  cones 
  having 
  their 
  apices 
  directed 
  toward 
  the 
  lateral 
  

   margins 
  of 
  the 
  valves. 
  On 
  the 
  dorsal 
  side 
  the 
  primary 
  lamellae 
  

   are 
  close 
  together, 
  but, 
  on 
  the 
  ventral 
  side, 
  they 
  are 
  wide 
  apart, 
  

   this 
  fact 
  indicating 
  that 
  the 
  bases 
  of 
  the 
  spirals 
  do 
  not 
  lie 
  in 
  

   prallel 
  planes 
  but 
  converge 
  toward 
  the 
  brachial 
  valve, 
  so 
  that 
  

  

  56 
  

  

  