POTERIOCRINID.E PENTACRINUS. 117 



2 Species. Pentacrinus Johnsonii. (Austin.) 

 Plate 15, Fi</. 1 (t, to c. 



Description. — The plates composing the body of tliis species agree in number and 

 position with the generic definition. The rays are long and taper, and apparently 

 forty, or upwards, in number. The column is long and slender, the elaspers circular, 

 and placed in series of five round the column, with considerable intervals, between 

 each series. 



Synonymes and References. 



Pentacrinites Johnsonii. — Aust. Ann. Nat. Hist. vol. 10, p. 109. 

 — Morris, Cat. Brit. Foss., page 56. 

 gracilis. — Charlesworth, Lond. Geol. Journ. No. 2, PL 9, page 96. 



Localities. 



The Inferior Oolite ? Bridport, Dorsetshire ; and in the Lias, at Staithes, near Whitby, 

 Yorkshire. 



The exact relation of the stratum at Bridport in which this Pentacrinus occurs, has 

 not, we believe, been satisfactorily determined. Some Geologists consider it as occur- 

 ring in the lowest bed of the Inferior Oolite, while others refer it to the upper bed of 

 the Lias. 



This beautiful Pentacrinus is remarkable for its slender and graceful form, every part 

 exhibiting the greatest neatness and delicacy of structure. The body is small, the rays 

 long and taper and closely set with delicately fine tentacula. The five main or primary 

 rays bifurcate at the second or third joint from the ray-bearing pieces. At a consider- 

 able distance from the first bifurcations they again branch out into pairs. A third 

 subdivision takes place still higher up, and there is some indication of even a fourth 

 bifurcation, but none of the specimens yet obtained prove this fact sufficiently distinct 

 to warrant us in deciding the point with certainty. 



The rays, if we estimate each of them as branching thrice, amount to forty, but if 

 the final subdivisions are four, the total number will be eighty. No other Pentacrinus 

 has such delicate slender arms as this elegant and well-preserved species. The rays, as 



