VON BUCH ON THE CYSTIDEA. 35 



surrounded with small plates since they do not remind one in the 

 least of arms. All the plates are distinctly marked with concentric 

 striae of growth, but it is a remarkable and striking fact that there is 

 no trace whatever of rhombic striae. 



Yet more striking however is the symmetrical and beautiful ar- 

 rangement of the ambulacral pores upon the surface. From the 

 middle of each lateral plate a double row of pores proceeds towards 

 the vertical angle, and a single row towards the angles on each side 

 of it, but on the lower half of the plate there are no distinct rows, 

 but merely detached pores irregularly distributed. With regard 

 however to the plates which form the summit, the case is just re- 

 versed, the lower half having rows and the upper half being without 

 them, while here also, as in the lateral plates, the middle row is 

 double and the others single. The upper part of the cup is thus 

 decorated with a festoon of these pores, as we have already seen was 

 the case in Caryocrinites, and the rows on the upper plates are in 

 the same way covered by small vesicles which conceal the orifices. 

 There is this difference however to be observed, that in the species 

 we are now describing none of these vesicles and ledges can be seen 

 between the rows of pores, which in the Caryocrinite ultimately 

 divide the whole plate into six deeply-marked triangles. 



The pores on the basal plates are hardly arranged in perceptible 

 rows, but there are many irregularly distributed over the surface. 



This remarkable and beautiful species appears not to be very 

 common. It has been found at Pulcowa. M. Blasius has obtained 

 it from Narowa near Narwa, and M. Eichwald mentions it also as 

 occurring near Reval. 



Genus SYCOCYSTITES. 



Sycocystites angulosus vel Senckenbergii, H. v. Meyer. 

 \_Echino-encrinus Senckenbergii, Herm. v. Meyer. Kastner, Ar- 

 chiv fiir die Naturlehre, Bd. vii. S. 185. tab. 2. fig. 1-5. Bronn, 

 Lethaea, tab. 4. fig. 1 . Echinosphcerites angulosa et striata, Pander, 

 tab. 2. fig. 27-31. VoUborth, Bulletin Scientifique de I'Acad. de 

 Petersb. x. n. 19. tab. 1. 7-12. tab. 2. Bullet, de I'Acad. 184.4. 

 t. 3. n. 6.] 



Plate III. fig. 7. Plate IV. fig. 3, 4. 



The determination of this genus long rested upon the evidence of 

 a single specimen, which has since disappeared and cannot now be 

 referred to. M. v. Meyer has however described it so well and so 

 distinctly that no doubt is left as to its peculiarities, and a specimen 

 has been since clearly and well figured by M. Vollborth of St. 

 Petersburg. Through the efforts of M. Kranz also, several speci- 

 mens have at length (November 1844) been received at Berlin, so 

 that now everything is obtained that can throw light on the investi- 

 gation of this very remarkable species. 



From all the Cvstidea hitherto met with, the present is at once 



d2 



