410 Prof. Beyrich on the Base {Pelvis) 



in accordance with a dorsal axis, the two axes have a normal 

 position towards one another. 



2. If the interradial pole of the radial axis be turned for- 

 wards in the reversed position of the calyx, or hind wards in 

 in its erect position, and, starting from the interradial pole, 

 we distinguish the lateral radii and interradii as adjacent and 

 abjacent, the following law applies to all Brachiata, namely, — 

 that the dorsal axis runs either from the right adjacent radius 

 to the left abjacent interradius, or from the right adjacent in- 

 terradius to the left abjacent radius. 



3. In the Brachiata with a pentagonal tripartite base, 

 whether monocyclic or dicyclic, the dorsal axis goes from the 

 right adjacent radius to the left abjacent interradius. PJaty- 

 crinus and Taxocrinus and allied genera were examined. 



4. In the monocyclic quadripartite base of Melocrinus the 

 dorsal axis goes from the right adjacent interradius to the left 

 abjacent radius. 



5. In genera with quadriradiate and triradiate stems {Cu- 

 pressocrinus, Gastrocoma^ and allied genera) the rays of the 

 stem are so arranged that they would cut into the segments of 

 a base divided either quadripartitely or tripartitely in accord- 

 ance with the observed axial directions, in an antimeral direc- 

 tion. 



6. The hexagonal base of Actinocrinus^ Hexacrinus^ and 

 Dichocrinus is symmetrically divided, as one of the dividing 

 sutures, starting from the dorsal pole, runs to the single inter- 

 radial side of the hexagon. 



7. In the Blastoidea {Pentatremites, Elceacrinus, and Codo- 

 naste?') the dorsal axis of the pentagonal tripartite base runs 

 from the left adjacent radius to the right abjacent interradius 

 — a position which lias not been observed in the Brachiata. 



8. The genus Stephanocrinus, which is referred to the 

 Cystidea, has the same position of the dorsal axis as the 

 Blastoidea. 



9. If we look at the Cystidean genus Cryptocrinus in the 

 same way as at a Brachiate Crinoid with a tripartite base, its 

 dorsal axis corresponds with a position from the left adjacent 

 interradius to the right abjacent radius. 



In conclusion, the question may be touched upon, how far 

 there are analogies between the peculiar division of the base 

 in the Crinoids and the symmetrical development of other 

 Echinoderms, especially the sea-urchins. 



Of the parts of the EcMnus-^Yi^W arranged in meridional 



