NATURAL SCIENCES OF PHILADELPHIA. 337 



really the case, and that the apparent central opening was closed by vault 

 pieces when the specimen was entire. 



Of the American species presenting, so far as known, the characters of this 

 genus as properly restricted, the following examples maybt mentioned, though 

 the vault of only the first two of these species is yet known to us, viz., C. mal- 

 vaceus, Hall, C. Iowensis,0\ven and Shumard, C. [Poleriocrinus) Barrisii, C.vimi- 

 nalis, C. lamellosus, C, divaricatus and C. rotundatus, Hall ; also C. Saffordi and 

 perhaps C. Farleyi, M. and W., and C. riffidus, White. 



N'ew species. 

 Cyathocrimites fragilis, M. and W. 



Body subsphffiroidal, a little oblique, rather regularly rounded to the column 

 below, from near the middle, and a little contracted above ; composed of remar- 

 kably thin plates. Facet for the attachment of the column not excavated and very 

 small. Base having the form of a very shallow, subpentagonal basin; basal 

 ])ieces with a general subquadrangular form, but really pentagonal, from the 

 slight truncation of their smaller inner ends at their connection with the column. 

 Subradial pieces comparatively large, hexagonal, excepting the one on the 

 anal side, which is larger than the others and heptagonal in outline. First 

 radial pieces rather smaller than the largest subradials, somewhat wider than 

 high, with a general subpentagonal form ; all strongly incurved above between 

 the free radials ; facet for the reception of the second radials about one-third 

 the breadth of the first radials and rather deeply excavated. Anal piece rather 

 smaller than the first radials, longer than wide, irregularly hexagonal and sup- 

 porting the outer side of the ventral tube (proboscis), which, like the body, is 

 composed of very thin plates. Second (first free) radials very small, short 

 and not always extending entirely across the excavation for their reception ; 

 succeeding radials, excepting the last, quadrangular, as viewed on the outside, 

 about twice as wide as long, and abruptly rounded or subangular on the out- 

 side ; last one pentagonal and generally a little longer than the others. Of 

 these free radials four may be counted in one of the posterior rays, six in the 

 other, three in one of the lateral rays, and seven in the anterior ray. 



Arms at their origin on the last radials rather divergent, and in one of the 

 posterior rays seen to bifurcate on the sixth piece, above Avhich one of the 

 divisions can be traced to the sixth piece without farther bifurcation, though 

 there are probably other divisions beyond ; arm pieces about as long as wide, 

 and, like those of the free radials, all deeper than wide, and pi'ofoundly 

 grooved within for the reception of the ambulacral organs. Surface smooth 

 or only very finely granular. 



Height of body, 0-50 inch : greatest breadth of same, about 0-75 inch. 



This species is related to C. rotimdattis, Hall, but not only differs in having 

 its free radial series much stouter (judging from the facets for their reception 

 in the tj-pical specimen of that species now before us), but in having all of its 

 body plates very decidedly thinner, while its first radials also diifer in curving 

 strongly inward, between the bases of the free rays. It likewise comes from 

 the lower division of the Burlington beds, while the rotundatus came from 

 the upper, and it has been found that scarcely any of the species are common 

 to those two horizons. 



Localitfi and position. — Burlington, Iowa ; lower part of Burlington limestone. 

 Mr. Wachsmuth's collection. 



Cyathocrinites tenuidactylus, M. and W. 

 Body, exclusive of the free rays, deeply cup-shaped, rounded below, com- 

 posed of moderately thick plates for a true Cyathocritius. Column compara- 

 tively rather stout, composed near the base of alternately thin and somewhat 

 thicker pieces, the latter of which project a little and seem to show a slight 

 tendency to become minutely nodular ; central canal distinctly peiitapetalous 

 in the form of its cross section. Base unknown (being accidentally shoved 



1868.] 



