[086]

Figs. l. 2. Upper parts of two nearly entire specimens of Briarean Pentacrinite, projecting in high relief from the surface of a slab, nearly two inches thick, [087]  and entirely composed of a mass of petrified Ossicula of the same species of Pentacrinite. The surface of these fossils is covered with a delicate film of Iron Pyrites, which gives them the appearance of beautiful Bronze. (Original.)

1^a. Continuation of the stem of Fig. l.

2^a. Portion of the stem of Fig. 2.

The length of these stems when entire, was three or four times that of the fragments here remaining.
Upon the stem 2^a, nearly all the side arms retain their places in the grooves on each side of the salient angles of the pentagonal column; they diminish in size as they approach its upper extremity. This is also distinctly seen at the upper end of the column of Fig. l.
a/F. First costal plate. b/F. Second costal plate.

Fig. 3. Portion of a third column retaining nearly all its auxiliary side arms in their natural place.

Fig. 3^a Continuation of the same column deprived of the side arms.

Fig.4 . Portion of another column, with traces of a few side arms rising from the lateral grooves.

Fig. 4^a Continuation of Fig. 4.

Fig.5. Fragment of another column, the joints of which are so much bent without dislocation, as almost to give the column the appearance of a spiral disposi tion.

Fig.6. Body of a Briarean Pentacrinite and summit of its column, shewing the interior of the ossicula that surround the abdominal cavity.

E. Pelvis. a/F First costal Plate. From a specimen in the
Oxford Museum. (Original.)

Fig. 7. Fragment of a column in the collection of Mr.
J. Sowerby, shc~'ving the obliquc articulation of the 088] base of the side arms, with the larger joints of the vertebral column. See V. I. p. 439. Note. (Original.)

Fig. 8. Magnified Section of a portion of a Column in the Oxford Museum. The joints, as in Pl. 52, Fig. 4, 5, and in Pl. 49, Figs . 3, 4, are alternately thicker and thinner; with a third, and still thinner joint interposed between them. See V. I. p. 435, Note. (Original.)

Fig. 8^b. Nat. size of Fig. 8.

Fig. 8^a. Portion of a Column, shewing the manner in which the edges of the thinnest plates, c, are visible along the salient angles only. In the intermediate grooves the thicker plates, of the first and second sizes, a, b, overlap and conceal the edges of the thinnest plates, c. The principle of this mechanism is the same as in Pentacrinites subangularis,Pl. 52, Figs. 4, 5, and in Encrinites moniliforinis, Pl.49, Figs . 3, 4; but the circular form of the column in the latter, causes the smallest plate, c, to be visible around its entire circumference. See V. I. p. 435, Note. (Original.)

The bases of two side arms are seen in two of the grooves, articulating with the uppermost large joint of this column. On other large joints are seen the sockets from which similar side arms have fallen.

Figs. 9, 10, 11, 12, 13. Various stellated forms on the articulating surfaces of Vertebræ, preserved in the dislocated mass beneath Figs. 1, 2. These petal-shaped, and crenated rays were probably adapted to produce various degrees of flexibility, according to their respective places in the column. The small Vertebra on Fig. 13, is derived from another individual. (Original.)

The aperture at the centre of all these Vertebra was for the passage of the alimentary canal, which [089] Miller considers to have sent off ten branches at every joint, five to the interior and five to the exterior of the petals.

Fig. 14. One of the largest auxiliary side arms.
Some of these contained more than 100 joints. See V. I.
p. 438. (Goldfuss.)

a, b. c. represent different forms of the joints at different parts of the side arms, with their nicely adjusted articulating surfaces.

Figs. 15, 16, a, b, &c. Various modifications of the articulating surfaces of the joints composing the fingers and tentacula. (Goldfuss, Pl. LI.)

Fig. 17. Magnified extremity of one of the tentacula. The two last joints form a very delicate pair of pincers, to lay hold on its prey. (Original.)