THE CYSTIDEA 



61 



Brachioles clustered round mouth, probably five, slender, and comparatively 

 long. Schizocystis, Jaekel (1895), Silurian, England. Type, Echinoencrinus 

 armatus, Forbes (Figs. XXV. -XXVII.). Arrangement of plates and rhombs 

 as in Pmnocystis ; rhomb 12 & 18 sometimes absent. Ant., r. ant., and 

 1. post, food-grooves almost or entirely atrophied ; 1. ant. groove extends 

 nearly half-way down the theca on to plate 11, is floored with alternating 



fp 



Br 



XXV. 



FIGS. XXV. & XXVI. 



ScMzocystis armatus' (from 

 Brit. Mus., E7589 & E7590). 

 x 2. XXV. from above; 

 XXVI. from the abanal 

 side. As, anus ; lir', facets 

 for brachioles ; fp, flooring 

 plates of subvective groove ; 

 in Fig. XXVI. the impressions 

 of these are seen in the distal 

 part of the groove ; Rh, the 

 pectinirhomb of plates 14 & 

 "15 ; St, part of stem. 



XXVI. 



Fio. XXVII. 



Analysis of Schizocystis. Plates 11 & 13 

 are notched by the food-grooves. Plate 23 is 

 double, and bears hydropore and gonopore. 



plates, bears about five brachioles ; a similar extension of r. post, 

 groove to plate 13 is checked by anus, and bears only three brachioles. 

 SUB-FAMILY 2, CALLOCYSTINAE, starts from a form in which all five sub- 

 vective grooves, with the usual flooring plates and brachioles, pass over 

 the theca, as in Lepadocystis ; and diverges (a) by suppression of grooves, 

 without branching, into Lepadocrinus and Pseudocrinus ; (6) by branching 

 of grooves, with subsequent suppression, into Callocystis, Sphaerocystis, and 

 Strobilocystis ; pectinirhombs 1 & 5, 14 & 15, 12 & 18 probably always 

 present. Genera - Lepa- 



Q. 



rv~ 



docystis, P. H. Carpenter 

 (1891 ; syn. Meekocystis, 

 Jaekel, 1899), Ordovician, 

 Indiana (Fig. XXVIII.). 

 Theca ovoid ; plates around 

 anus slightly altered from 

 the archetypal position. 

 Pectiuirhombs on 1 & 5, 

 12 & 18, 14 & 15, and 

 10 & 15. Main grooves 

 five, stretching a short dis- 

 tance over theca, one to 

 each plate of fourth circlet. 

 Lepadocrinus, Mather 

 (1843?; Conrad, 1840; Hall, 

 Staurocystis, Haeckel, 1897 ; 



FIG. XXVIII. 



Analysis of Lepadocystis Moorei, based on Meek's figures 

 (1871 & 1873). Plates 15 to 19 notched by food-grooves ; 

 hydropore on plate 23. 



1859 : synn. 

 ? Hallicystis, 



Apiocystis, Forbes, 1848 ; 

 Jaekel, 1899 ; includes 



