VON BUCH ON THE CYSTIDEA. 33 



The mouth («) in the middle of the summit, which is always 

 somewhat depressed, is elevated above the surrounding plates, but 

 not by a true proboscis. The round anal orifice is close by, and, 

 as in the Sphaeronite, is placed on the right side of the ovarial 

 aperture. 



It must be considered as a remarkable character of this species, 

 that the plates are not only entirely covered by the rhombic striae, 

 but so completely hidden by them that the lines of division between 

 the plates are only to be made out when the surface has been deeply 

 worn and rubbed. As, however, almost all the plates are hexago- 

 nal, the rhombic striae, which follow the same law in the Cystidea 

 that they do in the Crinoidea, and are invariably at right angles to 

 the edges of the plates, form thus six rhombs proceeding from the 

 centre of each plate, this central point being sometimes consider- 

 ably elevated. 



The genus Caryocystites, which we are now considering, has only 

 been found hitherto in Sweden, at Bodahamn in the northern part of 

 Oeland, and at Wikarby and Furudal in Dalecarlia. There is little 

 doubt however that it may also be found near St. Petersburg. 



4. Caryocystites testudinarius, Hisinger. \_Sph(Bronites tes- 

 tttdinarius, Hisinger, Lethaea Suecica, tab. 25. fig. 9. d.~\ 



Plate III. fig. 5. 



A singular form, which can hardly be identified with the last 

 species. The cylindrical cup is so greatly elongated towards the 

 two extremities, that the body almost disappears in comparison. 

 It is a Sphaeronite whose stem and proboscis are swelled out to mon- 

 strous proportions. 



The body itself consists of very large hexagonal plates : they are 

 much larger than those which enclose the Sphaeronite, and consist 

 of three rows alternating with one another, each row comprising six 

 plates. The rhombic striae on the surface are delicate, and do not 

 conceal the divisions of the plates. It is almost certainly the case, 

 that here, as in the other species, the pelvis is composed of four 

 basal plates of unequal size, but this is diflncult to make out di- 

 stinctly, and the more so because little plates continue to cover the 

 thick stem quite to its extremity, where a minute projecting point 

 proves that besides this there was also a very slender pedicle attached, 

 which served to fasten the animal to the ground. Five sharp pro- 

 jecting edges, traces of concealed arms, which are lost in the upper 

 part, may be distinctly seen indicated in both the stems. On the 

 upper side of the principal body, opposite to the pedicle, the some- 

 what remarkable pentagonal ovarial opening may be clearly distin- 

 guished. 



The proboscis is scarcely smaller than the cup itself, and large 

 plates enclose it quite to the extremity. Its length exceeds that of 

 the cup, and contributes very nmch to produce the monstrous ap- 

 pearance of the whole animal. Quite at the top the usual broad 



VOL. ir. — part II. D 



