KONGL. SV. VF.T. AKADEMIENS HANDLINGAR. BAND. 19. N:0 7. 



65 



aspect, and distinct from the interradia by a faint lineai- impression, discernible in the 

 largest of the specimens examined only; above it the caly.K is sliffhtly raised. The central 

 ossiole, or what raay have filled its place, is löst, and a nearly pentagonal open space is 

 left in the centre, or rather anteriorly. The tive costals are verv large, the posterior one, 5, 

 somewhat smaller than the others; they are all hexagonal, with the outward side slightly 

 truncated for the reception of the narrow middle plate of the corresponding interradium. 

 The costals 1 and 3 each bear a slightly tubular pore, apparently sexual, placed towards 

 the inner mai"gin. Water-pores were not to be found. The radials ai'e pentagonal, each 

 contiguous to the top of an ambulacrum; there is no trace of an ocular pore, if this be not 

 marked by a slightly larger granule observable in two or three of them. The whole 

 calyx is covered with a dense granulation similar to that of the interradia, but without 

 any indication of linear arrangement. The whole, costals and radials, appears as if 

 of one piece, the sutures being excessively fine, and to be elicited only by the treat- 

 ment mentioned above. The relative magnitude of the entire 

 system, the prominent share it takes among the constituents of 

 the skeleton, the forms and proportions of its parts, are such as 

 forcibly to recall the calyx of some Pala?ocrinoid, and to justify 

 a desire to turn the Echinoid upside down and to see the 

 calycinal system in its imaginary original position, when it form- 

 ed a part of some remote ancestral type. In this aspect the 

 resemblance becomes still more striking. 



In the remarkable group of the Saleniada?^) the three con- 

 stituents of the calycinal system, the central pentagon, the 

 costals, and the radials, are all simultaneously persistent in the 

 adult. The madreporite, the sexual openings, and the organs of vision, are in pos- 

 session of their respective ossicles. The system is generally seen to expand largely, 

 covering a gi'eat extent of the dorsal surface, and to exhibit, in forms of Mesozoic 

 existence, a highly elaborate sculpture, repeating almost every characteristic observed in 

 the calyx of Crinoids of preceding, Pala^ozoic, ages, but apparently of none from låter 

 times, as though in token of a common descent, and a yet not very remote epoch of 

 separation. The granulation seen in Acrosalenia, the deep impressions crossing the 

 sutures in Peltastes, the strong straight ridges connecting the centres of the ossicles 

 in Goniophorus, the impressed points at their sutures and angles in Salenia, often 

 continued on either side into parallel lines, are features well known in the Palasocri- 

 noidea and present also in the Cystoidea, but evanescent in the Crinoidea of Secondary 

 and låter ages. 



In the oldest of the known genera, Acrosalenia"), the periproct at first but 

 slightly touches the central disk or even fails to attain it. Placed closely within the po- 

 sterior margin of the costal 5, its large aperture is widened lengthwise, sometimes leav- 



Tiarechinus princeps Laube, with 

 the mouth upwards. 



1) Étndes, p. 27, 70, 78, pl. XIX, fi?. 177: XXI. 



-) It is hardly necessary to mention that the figuves here given are taken from the works of M. Cotteau 

 in the »Paléontologie Franpaise» and elsewhere, all unsurpassed models of research and elucidation. 



K. Sv. Vet. Akad. Handl. Band 19, X:o 7. 9 



