216 



NEW GENERA AND SPECIES OF CYSTIDEA. 



1854.] 



lar apparatus of small plates ; anal orifice on the left side, near the 

 mouth; ovarian aperture in the lower half of the body, without 

 valves; column short, and tapering to a point downwards; pec- 

 tinated rhombs on many parts of the body. 



But one species is known, which is the following : 

 Glyptocystites Multipora. 



DIAGRAMS OF THE STRUCTURE AND ARRANGEMENT OF THE PARTS.* 



I Fig. 1. Fig. 2. , tj Fig. 3. Fig. 4. 



Left side. 



Posteal side. 



Rigid side. 



Anteal side. 



\ ¥ 



Fig. 5. 



Fig. 6. 



JYo:l 



Development of the plates and pores of 

 of Glyptocystites mitftipora. 



Development of the plates and pores 

 of Sycocystitcs (Echino-enerinites) 

 angutosus, as drawn by Von Buch. 



— Quarterly Journal, Geographical Society, Vol. II, Plate 4. 



This beautiful little fossil is about one inch long, and five-eighths 

 of an inch in its greatest diameter. Some of the specimens are 

 larger, but these appear to be the average dimensions. The body 

 is of an oblong and slightly conical shape, most obtuse at the base. 

 It is also obscurely five-sided, the arms being situated upon the 

 angles. Its covering consists of a number of polyhedral plates, 

 firmly united at their edges, and forming a strong calcareous shell, 

 which, if fissured down from the top to the bottom, and unfolded 

 on a plane surface, would present the arrangement seen in Fig 5. 



In the several other genera of Cystideans allied to this, the rows 

 of plates extend in uninterrupted bands horizontally round the 

 body, but here the second and third rows are broken through by 

 the extension of the plates in the series below and above. 



In the basal series there are four plates resting upon the upper 

 joint of the pedicle, one of them hexagonal, and three pentagonal. 

 The hexagonal plate occupies the base on the posterior side, and 

 supports that plate on which rests the ovarian aperture ; and the 



* The side containing the large ovarian aperture may be considered as the posterior 

 side of the animal, and consequently the right and left sides will correspond with the 

 right and left hands of the observer, while the anterior side will be directly opposite or 

 in front. 



pentagonal plate, immediately opposite on the front side of the 

 fossil, is remarkable for being twice the height of the others. As 

 allusion will be frequently made to it in the course of the follow- 

 ing description, it is marked No. 1 in the diagram Fig. 5, for con- 

 venience of reference. 



The second series consists of five plates, three hexagonal, and 

 two slightly heptagonal. This row is divided in front by the great 

 extension upwards of No. 1. The ovarian aperture rests in a con- 

 cave notch excavated out of the upper side of the plate in this 

 series, which is supported by the hexagonal pelvic plate. These 

 two rows enclose the lower one-third part of the body. In the 

 third series a small but conspicuous hexagonal plate occupies the 

 front, resting on the apex of No. 1, and having a small pentagonal 

 plate on its right, or on the left side of the fossil. On the right 

 side is a large rhomboidal plate, made heptagonal by being notched 

 on its lower side to fit upon the angles of the two plates below, 

 one of which it covers in part, the others entirely. This plate is 

 easily recognised by the large pectinated rhomb between it and 

 the ovarian aperture, and by the diagonally-placed rhomb, which 

 lies partly across the fossil at the upper side of the plate in question. 

 It is separated from the small hexagonal plate by a projection of 

 one of the plates of the fourth series, which here rests upon a plate 

 of the second. Two other partly rhomboidal plates of this series 

 enclose the sides of the ovarian aperture, and meet over it. 



The three last-mentioned plates of the third series are each in 

 height about one-third of the total length of the fossil, and resting 

 upon them are three plates of the fourth series of nearly the same 

 size and shape, which extend to the line of the origin of the arms. 

 The other two plates of the fourth series are more than half the 

 whole length of the body. One of them stands upon the small 

 hexagonal and pentagonal plates, and the other in part upon the 

 small hexagonal plate, and in part upon a plate of the second series. 

 All the plates of the fourth series are excavated on their summits 

 where the five arms originate from them. They do not close the 

 fossil at the top. The circular space surrounded by their upper 

 extremities is closed over by a dome, in the top of which is the 

 elongated mouth. 



The five plates in the second series, and in some of the speci- 

 mens the two small ones in the third, are ornamented by strong 

 rounded ridges, which radiate from the elevated centre of the plates 

 to the corners, or cross the sides at right angles. There are also 

 generally one or two short ridges between the rays, while some- 

 times several concentric lines of growth may be observed. 



The principal characters upon which the genera of Cystidea and 

 Crinoidea have been established, are derived from the number and 

 arrangement of the plates between the base and those points near 

 the summit whence the arms arise. Many Crinoids, among which 

 may be mentioned, as affording good examples, the very ancient 

 Heterocrinus, several species of which abound in the same strata 

 along with the Cystidea now under examination, and also the recent 

 species, Pentacrinus Caput Medusce, living in the Caribbean Sea, 

 are formed simply of five vertical pillars of plates, which stand upon 

 the pelvis, and proceed straight up the sides of the cup to the top, 

 where each supports an arm. These, with many others that could 

 be cited, might be properly arranged into a family, in which the 

 distinctive feature would consist in the presence of those arm-bear- 

 ing pillars of more or less quadrangular plates, placed one above 

 the other. This structure appears, with some slight irregularities, 

 in the unfolded calcareous shell of Glyptocystites, as represented 

 in Fig. 5. 



As the arms may be considered simply as continuations upwards 

 of those pillars, and as the base of the fossil whence they arise is 

 the back of the animal, they (the arms) are said to be developed 



