of the Crinoidea brachiata. 



407 



figure on p. 405, but with tliis difference, that the inner angles 

 are equalized. 



Besides quadriradiate stems, stems with triradiate nutritive 

 canals also occur in two species of Cupressocrinus. One of 

 these species is frequent in the Eifel, and was characterized 

 almost simultaneously by L. Schultze as C. injiatus and by 

 Quenstedt as C. trimerus ; the second has been described by 

 Schultze as C. Meroglyphicus. On the examination of ten 

 calyces of C injiatus^ it soon appeared that here also the three 

 rays of the stem are not symmetrically placed with regard to 

 the radial axis ; but yet in the majority the position did not 

 correspond with the dorsal axis, which was the detenninant 

 for the quadriradiate stems. In the most regularly fomied 

 calyces one of the three rays appeared rather to be turned to- 

 wards the right adjacent angle of the pentagon of the central 

 plate — that is, in correspondence 

 with the axis which was de- 

 terminant for the symmetrically 

 tripartite base of Platycrinus 

 and the Taxocrinidge. In the 

 annexed figure the character is 

 illustrated in the same way as 

 that of the quadriradiate stem, 

 by drawing in the pentagon of 

 the central plate three segments 

 in accordance with the axis in- 

 dicated, so that the three rays 

 of the nutritive canal have the 

 antimeral position. 



Perhaps the deviations from the rules assumed for the stem 

 of Cupressocrinus^ which are comparatively not uncommon, 

 may be refen-ed to the occurrence of something like hesita- 

 tion in the selection of one or the other axis in the formation 

 of the stem. The proportion of abnormal to nonnal positions 

 in the observed cases is as follows : — in the quadriradiate 

 stems of G. gracilis three or four abnormal occurred to fourteen 

 normal, in C. ahhreviatus two abnormal to five normal, 

 and in C. injiatus three abnormal to seven normal. It must, 

 however, be taken into consideration here that few other ge- 

 nera have such a tendency as Cupressocrinus to produce nu- 

 merous and multifarious monstrous formations. 



The nearly allied genera Gastrocoma^ Ceramocriyius, Nano- 

 crinus^ and Lecythocrinus would be especially fatted for further 

 investigations upon the fundamental law of the quadriradiate 

 structure of the stem ; these all resemble Cupressocrinus in the 

 composition of the base. Among the materials in the Berlin 



