KONGL. SV. VET. AKADEMIENS HANDL. BAND 19. N:0 7. 



57 



of the geminous pores, as to cause the lineage of the ArchtBonomous Echinoidea to 

 gravitate forcibly towards that group of antique Cystoidea of the Silurian era, different 

 as these no doubt were in other respects, in the total absence, — at least in the 

 adult, — of a calyx, and in the distribution of the pores all över the perisome. 

 There seeins also to be little reason for doubting the pedicellar character of the 

 geminous pores in Sphseronis, Eucystis, Glyptosphasra, Protocrinus, Mesites, the less 

 so since the want of a decisive proof in this regard is supplied, in some degree at 

 least, by the occasional preservation of the 

 actual pedicels in a contemporary form of 

 Echinoids, Botryocidaris Pahleni Feed. Schmidt, 

 of the older Silurian era. A specimen of 

 this most remarkable type, for the inspection 

 of which I have to thank the liberality of 

 its learned author, distinctly shows, in several 

 places, long C3'lindroid bodies, having one 

 of their ends in close connection with an 

 ambulacral, geminous pore, even so as to 

 CO ver it, and for the rest of their length 



lying variously bent across the plates, with their free ends gradually tapering into 

 rounded tips, and thus like the simple pedicels of one of our Echinoids. They even 

 exhibit traces of having had their tubes strengthened by series of arcuated spicules. 

 The peripodia, so I venture to call them from analogy, of those archaic Cystoidea 

 and of Botryocidaris, and, generally, of the Archseonomous Echinoidea, are built 

 mainly upon the same model: a wall, more or less raised, incloses an elliptical or 

 lengthened depression in which, in the great majority of forms, two nearly equal per- 

 forations open, placed on the longitudinal diameter and separated by a septum, or 

 bridge, of varying breadth and form. 



Pedicels of Botryocidaris Pahleni Fk. Schmiut. 



U© . 



Sphceronis 

 pomum Gtll. 



Glyptosphtera 

 Leuchtenbergi Volb 



Peripodia. 



Protocrinus 

 fragum EicHW. 



Mesites 

 Pusirefskii NiK. 



In the genera of Cystoidea named 

 above, their distribution is somewhat 

 various. In Sphseronis and Eucystis 

 the whole perisome is densely crowded 

 with them, all or nearly all pointing 

 adorally with their longer axis; in 

 Protocrinus they are strewn less dense- 

 ly över the whole exteriör, the grooves excepted, and point mainly in the direction 

 of the mouth, still with a tendency to deviate; in Mesites they are confined to the 

 perisome and variously divergent. In Botryocidaris they are confined to the ambulacra, 

 and point all one way. This is also the case with the ambulacral peripodia in all the 

 rest of the Echinoidea, the direction of their longer axis being towards the mouth, 

 those of the branchial peripodia of the petala excepted, which normally are transverse. 

 In Pl. XII, Jig. 132—149, an attempt is made to give a general idea of some 

 important modifications of the peripodia among the Neonomous Echinoidea. The series 



8 



K. Sy. Vet.-Akad. Handl. Bd. 19. N:o 7. 



