﻿INVERTEBRATES. 
  327 
  

  

  Descriptions 
  of 
  now 
  Carboniferous 
  Echinoderms, 
  by 
  A. 
  H, 
  Worthen 
  and 
  S. 
  A. 
  Miller. 
  

  

  CLASS 
  ECHINODERMATA. 
  

  

  ORDER 
  ASTEROIDEA. 
  

  

  Family 
  PAL^EASTEEIDJE. 
  

  

  Compsastee, 
  n. 
  gen. 
  

  

  (Ety. 
  Kompsos, 
  elegant; 
  aster, 
  a 
  star.) 
  

  

  Body 
  stellate 
  ; 
  central 
  area 
  or 
  disc 
  comparatively 
  small 
  ; 
  rays 
  large, 
  

   long, 
  more 
  or 
  less 
  fusiform; 
  grooves 
  deep 
  and 
  bordered 
  by 
  numer- 
  

   ous 
  thin, 
  subcircular, 
  adambulacral 
  plates. 
  The 
  ventral 
  side 
  of 
  the 
  

   typical 
  species 
  shows 
  about 
  six 
  rows 
  of 
  plates 
  upon 
  each 
  side 
  of 
  

   the 
  ambulacral 
  furrows, 
  which 
  have 
  a 
  regular, 
  transverse, 
  as 
  well 
  

   as 
  longitudinal 
  arrangement. 
  

  

  This 
  genus 
  is 
  distinguished 
  from 
  all 
  others 
  in 
  the 
  family 
  by 
  the 
  

   number 
  and 
  form 
  of 
  the 
  adambulacral 
  plates, 
  by 
  the 
  great 
  number 
  

   of 
  disc 
  plates 
  upon 
  each 
  side 
  of 
  the 
  ambulacral 
  furrows, 
  and 
  by 
  the 
  

   general 
  form 
  of 
  the 
  body 
  and 
  rays. 
  

  

  CoMPSASTER 
  FORMOSUS, 
  Sp. 
  nOV. 
  

  

  PI. 
  XXXI: 
  Fig. 
  2 
  a, 
  ventral 
  side, 
  natural 
  size; 
  flg. 
  2 
  b, 
  section 
  of 
  a 
  ray 
  enlarged 
  two 
  di- 
  

   ameters. 
  

  

  Body 
  deeply 
  stellate 
  ; 
  central 
  disc 
  comparatively 
  small 
  ; 
  rays 
  rigid, 
  

   large, 
  fusiform, 
  more 
  than 
  twice 
  as 
  long 
  as 
  the 
  diameter 
  of 
  the 
  cen- 
  

   tral 
  disc, 
  and 
  terminating 
  abruptly 
  in 
  an 
  obtuse 
  point. 
  The 
  typical 
  

   specimen 
  furnishes 
  the 
  following 
  measurements 
  : 
  Diameter 
  of 
  the 
  

   body, 
  T 
  y 
  - 
  inch; 
  length 
  of 
  ray 
  from 
  central 
  part 
  of 
  disc, 
  I.jVo 
  inches; 
  

   diameter 
  of 
  the 
  ray 
  at 
  its 
  junction 
  with 
  the 
  body, 
  -fife 
  inch. 
  

  

  Ambulacral 
  grooves 
  deep 
  ; 
  ossicles 
  rather 
  small 
  ; 
  adambulacral 
  

   plates 
  very 
  numerous, 
  and 
  consisting 
  of 
  a 
  series 
  of 
  thin 
  plates 
  upon 
  

  

  1 
  1 
  

  

  