SAGENOCRINIDAE 24 1 



plates can be observed their position appears to be normal. The specimens of F. saffordi 

 have thrown important light upon the structures at the inner floor of the calyx, and the 

 orientation of the axial opening leading into the stem ; there are about 25 of them, all 

 thoroughly weathered out of the soft matrix, so that the original surfaces are well exposed. 

 At the inner floor of the inf rabasals the axial opening is surrounded by a thin partition which 

 arises and expands into a funnel-shaped vessel with three rounded lobes coinciding in posi- 

 tion with the infrabasals, each having a broad, shallow chamber leading down toward the 

 central opening (see various figures on Plate XXX). The lobe upon the small infrabasal is 

 of course radial ; while the other two, whose chambers pass in over the edges of the larger 

 infrabasals, are interradial. The stem lumen is quinquepartite, usually dividing into five 

 strongly petaloid lobes a short distance down. 



In order that the chambers of the three lobes of the funnel shall produce five channels 

 in the stem, two of them must be subdivided, and one would naturally expect that these 

 would be the two on the larger plates ; but that is not what happens. The lobe on the radially 

 situated infrabasal divides by means of a thin median septum into two chambers, which 

 encroach somewhat upon the other two lobes and pass down to an interradial position ; on 

 one of the others the chamber, already interradial, remains single and passes directly down, 

 while the third, also interradial, is likewise divided by a septum, one branch remaining in 

 its original position and the other diverging to the fifth, and before unoccupied, interradial 

 side (PI. XXX, figs. 3c, 5c, 6c, jb, and text-fig. 2a 1 ). Thus within the three lobes five smaller 

 channels are produced, all interradial, and they pass down into the stem in that position ; 

 they are at first not equal — the three opposite the infrabasal sutures being the largest, and 

 the other two considerably smaller (figs. 3a, 5a, c), but after passing into the stem they soon 

 become equal (figs. 6a, 9, 14). In F. agassizi the canals at a short distance below the calyx 

 appear to be generally interradial, although the orientation is indefinite in some specimens, 

 and this is probably the condition throughout the genus. 



The further taxonomic and nomenclatorial questions involving the relations of this 

 genus to Taxocrinus are complicated and difficult, and it will be necessary to state them at 

 some length in order to reach a conclusion which may seem fair : 



It has already been stated that De Koninck and Le Hon founded Forbesiocrinus upon 

 a form which they fully described and illustrated, but erroneously identified as Taxocrinus 

 nobilis of Phillips. In justifying their proposal of a new genus upon a supposedly already 

 described species, they undertook to limit Taxocrinus " to those species which do not pos- 

 sess interradials (interbrachials) but of which the calyx consists exclusively of basals, or of 

 those and the first radial pieces, such as T. macrodactylns Phillips, and T. (Cyathocrinus) 

 Rhenanus F. Roemer " (Recherch. Crin. Carb. Belgique, pp. 120, 121). This was not a 

 very happy suggestion, for not only does T. macrodactylus, one of the species cited by them, 

 have at least one interbrachial, but Phillips had included in his genus two other species not 

 mentioned by De Koninck and Le Hon which have it likewise. Therefore on this character, 

 upon which De Koninck and Le Hon chiefly relied, the separation of the new genus could 

 not be upheld. Phillips did not so limit his genus, as is evidenced by the species he ranged 

 under it; and M'Coy in redescribing it in 1854 (British Pal. Fossils, p. 53), definitely speci- 

 fied as a generic character under Taxocrinus, that " five hexagonal interradial plates intervene 

 between the second primary radials " ; and he laid stress on this, adding, " the interradial 

 plates and the separation of the primary radial rows seem to separate this genus from 

 Ichthyocrinns." 



In 1865 Meek and Worthen (Proc. Acad. Nat. Sci. Philadelphia, p. 138) discussed at 

 length " the genus Taxocrinus and its relations to Forbesiocrinus." They found the same 

 objection as above stated to De Koninck and Le Hon's definition, and concluded that the only 

 difference between the two then ascertainable was in the number of interradials, and not in 



