256 D. Echinodermata. 



Ichthyocrinidae are nearest related to the Cyathocrinidae , from which they 

 differ in having several orders of radials included within the body , in the arti- 

 culate structure of the radial portions , in the presence of interradial plates within 

 the regions of the calyx, and in the pliant vault." 



Fur die Familie der Cyathocrinidae wird folgende Diagnose gegeben : 



Calyx composed of only three rings of plates alternating with each other, each 

 ring composed of five plates; all succeeding plates free. The proximal ring or 

 imderbasals not unfrequently hidden from view by the column , perhaps in some 

 cases wanting, rarely anchylosed so as to form three plates or a single one. The 

 plates of the second ring generally varying in form , the posterior one frequently 

 truncate. Those of the third ring or the radials, more or less pentagonal , the 

 right posterior one often smaller on account of interposed anal plates. The suc- 

 ceding order of plates which have been generally designated as free radials, but 

 for which we have adopted the term brachials, consists of one to two or more by 

 five plates on which the arms originate. Arms simple or branching, comparatively 

 long ; either provided with rather strong pinnulae , alternately arranged , or , in 

 the absence of these, the ambulacral groove is covered with two rows of alterna- 

 ting pieces, more or less wedge-shaped, sometimes strongly cuneiform, and inter- 

 locking. There are from one to four anal plates within the calyx. When there is 

 a single anal, the symmetry of the body is generally bilateral, but, in case of two 

 or more, the form is irregular, because the plates tend obliquely toward the right 

 side of the body. The anal plates support a ventral sac, which is cylindrical, con- 

 voluted, club- or balloon -shaped, and which occasionally attains immense pro- 

 portions. The sac is bordered with rows of pores or fissures ; its upper extremity 

 closed, so far as observed ; the anal opening lateral. Interradial plates proper in- 

 tirely wanting. Calyx surmounted by five large oral plates, with a central ope- 

 ning between them, and forming at their sutures five shallow ambulacral grooves 

 converging toward the centre. Central opening covered by the apical dome plates, 

 and the five grooves arched over by two rows of small immovable pieces, alter- 

 nately arranged. Column round or pentagonal. The Cyathocrinidae differ from the 

 Ichthyocrinidae in having a solid inflexible vault , built up of oral plates ; in pos- 

 sessing but a single radial to each ray; and in the absence of interradial plates. 



Bei der enormen Fulle von Beobachtungen und kritischen Bemerkungen, welche 

 in den Beschreibungen der einzelnen Gattungen niedergelegt sind, miissen wir auf 

 ein ausluhrlicheres Referat verzichten und uns darauf beschranken die eine neue 

 Gattung mit ihrer Diagnose, sowie die drei neuen Arten aufzuluhren. 



Fur den von Schultze aus dem Eifeler Kalke beschriebenen Taxocrinus gra- 

 cilis wird eine ueue Gattung Rhopalocrinus aufgestellt mit folgender Diagnose : 



General form of body , including arms , subclavate , with bilateral symmetry ; 

 plates heavy. Underbasals three, scarcely visible beyond the column. Basals five, 

 four of them equal , regularly pentangular , the fifth much higher, becoming nar- 

 rower toward the top, truncated above for the accommodation of the proboscis. 

 Radials placed in a direct line with the arms ; one ring only constituting a part of 

 the solid body, all succeeding ones being more or less movable. First radial large, 

 heavy, the articulating face occupying almost the entire width of the plate , cir- 

 cular. facing slightly outward , and perforated with an opening which communi- 

 cates with the interior body and with a passage toward the dorsal side of the arms. 

 Second radials , or first brachial plates, wide but short , evidently movable , pro- 

 bably connected interradially (between the rays) by small polygonal plates. Suc- 

 ceeding plates all of the same width and form as those of the preceding ring ; 

 their height, however, three or four times greater. Arms five, simple throughout, 

 and closely resembling those of Symbaf/tocrinus ; length unknown , of almost uni- 



