POTERIOCRINID.E EXTRACRINUS. 107 



Synonymes and References. 



Briarean Pentacrinite.— Parkins. Oig. Rem. Vol. 2, PI. 18.///, 2, p. 252. 



— Knorr. Reciteil de Mon. suppl. t. II c. 

 Pentaciinites subangularis.— Mill. Nat. Hist. Crin. PI. \,p. 59. 



— Goldf. Pet. Germ. PL b%fig. \, a, to n, p. 171. 



Formation and Localities. 



The lias at Chedwick, or Chedcock, near Bridport; Lyme, Dorsetshire; and Boll, 

 Wurtemburg. 



A few specimens only of this beautiful species of Extracrinus have hitherto been 

 developed, consequently its geological range may be considered as confined within 

 narrow limits as compared with the preceding species. It seems to have first appeared 

 on the stage of life towards the close of the liassic period, and to have become extinct 

 at the physical change which gave rise to the succeeding or oolite group of rocks. 



The specimen from which our illustration is taken was long in the cabinet of the late 

 Mr. James Jolinson, and is now in the possession of the Rev. D. Williams, of Bleadon. 

 Another fine specimen now adorns the collection in the British Museum. Some finely 

 preserved portions of columns are also deposited in the Museum of the Bristol 

 Institution. The upper surface of one slab twelve inches by nine or ten, is a complete 

 congeries of the columns of this species, and shews that in some few instances these 

 animals were as thickly associated together as the more generally ditfused E. Briareus. 

 On the under side of this slab is the column represented in PI. 13, fig. 1, i. 



The arrangement of the calcareous pieces forming the body of this species of Extra- 

 crinus bear a general resemblance to that of the E. Briareus. The prolonged lateral 

 pieces are in most specimens jointed, while in others they rather appear as if soldered 

 together, but in either case they extend some distance below the dorso-central plate. 



The main, or primary rays are five, of two joints each, but somewhat shorter than in 

 the typical species. At each of the upper or cuneiform joints they branch off into a 

 pair making ten, these again subdivide, and as the leading rays of each group occupy 

 the outer flanks, the lateral or lesser rays emanating from the leaders occupy the central 

 spaces. 



