1854,] 



NEW GENERA AND SPECIES OF CYSTIDEA. 



217 



from the dorsal pole of the cuticular skeleton. Volborth, an emi- 

 nent palaeontologist, contends that it is so in the Cystidea, and that 

 they are true Crinoids, while several other writers upon the science 

 maintain an opposite opinion, and regard the arms of the Cystidea 

 as springing from the ventral aspect, arid being developed down- 

 wards. Upon this curious question I do not feel myself authorized 

 to venture an opinion, and shall content myself with directing atten- 

 tion to the fact that this new genus appears to be constructed very 

 nearly upon the same plan as the Crinoids above mentioned. 



The small cup of an Encrinite, figured at the end of this paper 

 for another purpose, is formed upon a different principle. The 

 plates of the second row alternate with those of the pelvis, and 

 those which bear the arms do not rest immediately upon single 

 plates below, but in the angles formed by the sloping sides of the 

 plates of the second series. There is no trace of the arm-bearing 

 pillars, as in Heterocrinus and Pentacriivus. It is a member of 

 a different family, in which the genera Cyathocrinus, Poteriocri- 

 nus, Homocrinus, and others of similar structure may be placed. 



In Fig. 6 is represented the structure of the Cystidean Echino- 

 encrinites, which is the same in principle as this family of Crinoids, 

 with alternating plates. This genus, and four others, Pseudocri- 

 nites, Pninocystites, Apiocystites, and Lepadocrinites, are all 

 constructed exactly alike so far as regards the plates below the 

 arms ; and as they are the only Cystideans yet known to which 

 Olyptocystites exhibits anything like a near approach, it must 

 for this reason alone be considered a new genus. 



The arms are five, four of them in perfect specimens extending 

 from the summits of the plates of the fourth series to the base, 

 and the fifth being only about three lines in length. They divide 

 the surface into four compartments, seen in Figs. 1, 2, 3, and 4. 

 The right side, Fig. 3, is nearly twice as wide as any one of the 

 others. It is divided at the upper part by the short arm. The 

 two arms on the ovarian side, Fig. 3, unite near the summit, and 

 the grooves which occupy their centres here unite, and cross over 

 the apex in a single furrow to the other side, where they separate, 

 and follow down the front pair of arms. A short groove also 

 from the apex extends to the lower end of the short arm. On 

 each side of each groove there is a row of seven or eight protu- 

 berances, which are the bases of the tentacles. 



On none of the Cystidea heretofore discovered are there more 

 than three of those organs called pectinated rhombs or ambulacra! 

 openings, while this species displays the extraordinary number of 

 thirteen. The office performed by them in the animal economy 

 has not yet been explained. They consist of spaces of small extent, 

 perforated by elongated pores, which pierce the plates to the inte- 

 rior. They are generally of a rhomboidal shape, and each is situ- 

 ated upon two plates, one half being upon each. In Glyptocy- 

 stites they differ somewhat in external appearance from those 

 described as belonging to the English and American Cystidea 

 already known, but correspond in form very nearly with those of 

 the Russian species of Echino-encrinites. In the Geology of 

 Russia, as quoted by Mr. Hall in Vol. I. Palaeontology of New 

 York, p. 88, it is stated : " The Echino-encrinites is further dis- 

 tinguished by the presence of pores, not disseminated over the 

 entire surface, as in Echino-sphmrites, but occupying a determinate 

 place, and bordering three small rhomboidal areas." This is their 

 form in Olyptocystites. There is in each a smooth rhomboidal 

 space, the length of which is twice the breadth, and completely 

 surrounding it is a row of elongated pores. The suture between 

 the two plates, upon which each of those organs is situated, forms 

 the greatest diagonal of the rhomb. These pores do not terminate 

 at the border of the smooth space in the centre, but are extended 

 beneath it, and cross over to the other side. I ascertained this 

 2 



fact by grinding down the surface of a specimen. When the tin- 

 perforated space in the centre is thus removed, these rhombs are 

 precisely similar to those of one of the species of Pleurocystites, 

 presently to be described in this paper. 



The several positions of these rhombs are as follows : 



On the left side of the fossil, Fig. 1, there are two, one of which 

 extends from the centre about half way to the summit, inclining 

 towards the rear as it ascends, with a very small one immediately 

 above it, and inclining to the front. It must here be noticed that, 

 in all the large rhombs of this species, there is an elevated border 

 along one side of the unperforated area in the centre. In this 

 compartment the border is on that side of the large rhomb which 

 corresponds with the left hand of the observer. 



On the ovarian side, Fig. 2, two are visible, a small one under 

 the left side of the aperture, and a large one, with the border on 

 the left, standing perpendicularly above it 



On the right side, Fig. 3, there are five : 1st. A large one upright 

 along the left side of the division, in length one half that of the 

 fossil, and with the border on the right : 2nd. A small one perpen- 

 dicularly above the upper end of the last : 3rd. A third lies across 

 the fossil from the top of the large one, but inclining downwards, 

 and with its border on the lower side: 4th. The fourth extends 

 from the lower end of the third nearly to the summit; its border 

 is on the right : 5th. The remaining rhomb on this side appears 

 to be half of a large one. It consists of two rows of pores, united 

 a little below the centre on the right side of the division, and spread* 

 ing apart from each other in the direction of the point above, where 

 the two last mentioned touch each other at then lower extremities* 



On the front side of the fossil, Fig. 4, there are four of those 

 rhombs, two of which occupy precisely the same position as two 

 of those on the Russian species of Echino-encrinites. Referring 

 again to the Geology of Russia, we find it stated : " Two of these 

 poriferous rhombs are situated near the base, and have their great* 

 est diagonals united upon one of the angles of the opening where 

 the stem is inserted, while the third is found on the opposite side 

 between the mouth and the great lateral opening, and directly above 

 the pentagonal basal plate. The two first are mounted upon plates 

 of the two inferior ranges, and the last upon those of the two 

 superior ranges." In Glyptocystites one half of each of these two 

 rhombs is situated on the elevated basal plate No. 1, and the other 

 halves on the plates of the second range, which lean against its 

 long, sloping sides. In each the border is on the upper side. By 

 referring to Fig. 6, it will be seen that Von Buch has figured them 

 in the same position, with the exception that there the greatest 

 diagonal is at right angles to the suture between the plates. In 

 this fossil, the greatest diagonal in all the rhombs follows the suture, 

 arid the lesser diagonal crosses it. In the English species of Echino- 

 encrinites there is but one rhomb below and two above, while in 

 the Russian fossils the reverse is the case. The true form and dis- 

 position of those organs, as described by Von Buch, and by the 

 authors of the Geology of Russia, although alluded to, have evi- 

 dently been overlooked in the English and American works before 

 referred to. On the right side of the small hexagonal plate in 

 front there is a very small rhomb, and, with its greatest diagonal 

 running perpendicularly upwards from the centre of the upper side 

 of this plate to the top of the plates of the fourth series, there is a 

 very large one with the border on the left side. 



The whole of the lower part of this fossil to the top of the second 

 series is exactly like Echino-encrinites angiilosus, as described by 

 Von Buch, with the exception of the great height of the basal 

 plate No. 1. He says: "The stem is very slender at its further 

 (lower) extremity, and is provided with articulations, whose length 



