SILURIAN RADIATA. 177 



I have not distinctly made out the interhraehial plates, but 

 as there seems a notch between the upper adjacent edges of the 

 scapula), I have little doubt they existed ; besides their presence, 

 the species is easily distinguished from the Ichthyocrinus pyri- 

 formis (Phili. sp.), by the greater number of joints in the arms 

 and hands, the much thicker column, and the nearly unvarying 

 character of the joints as they approach the pelvis. 



In the " Asterias " bed of the Upper Ludlow at High Thorns, 

 Underbarrow. 



{Col. University of Cambridge.) 



Glyptocrinus basalis (M^Coy). 



Sp. Char. Cup subpyriform, pelvic plates hexagonal, slightly 

 exceeding the costals in length and supporting the intercostals 

 on their upper truncated edge; all the plates marked with 

 thick radiating ridges, one to each side, except in the pelvic 

 plates, which have them only in the three upper sides, the 

 lateral pair being the forked ends of the strong vertical ridge 

 of the costal or radial rows ; average length of cup from pelvis 

 to base of rays, 1 inch 6 lines ; width the same ; length of pelvic 

 plates 3i lines, pentagonal first costal 3 lines, hexagonal second 

 costal 2~ lines, heptagonal scapular plate 3 Imes, hexagonal 

 first arm plate 2^ lines, second arm plate 2 lines. 



This fine species difi^ers from the Glyptocrinus decadactylus 

 (Hall), of the Hudson River group of New York, by the great size 

 of the pelvic plates, and their being hexagonal instead of penta- 

 gonal, and their bearing the intercostal plates directly on their 

 truncated upper edge, the intercostals in the American species 

 being supported on the sides of the laterally united first costals, 

 which latter plates in this species are completely separated. The 

 first arm-plates are laterally united without the intervention of 

 an interbrachial plate, which exists however between the second 

 arm-joints, nearly equaling them in size. In one of the most 

 distinctly preserved intercostal spaces, three interscapular plates 

 are seen to rest on the upper half of the octagonal intercostal, 

 the lateral ones being pentagonal, and the middle longer one 

 hexagonal. A\\ the plates seem to have been thin, and allow 

 considerable variety in form of the cup from slight pressure. 



Not uncommon in the calcareous schists of Alt yr Anker. 



(Col. University of Cambridge.) 



M 



