126 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



in some, there seems reason to infer the existence of an elongate 

 proboscis. 



In Lyriocrinus we have a subglobose body, with the basal plates 

 extremely rudimentary, and not noticed in the original generic 

 description, though since proved to exist. The interradial plates are 

 four or five, with a single interbrachial plate; the arms rising in 

 pairs from each ray, and continuing simple to their extremities. 

 Dome unknown. 



In AcANTHocRiNus, thc ba§al plates are developed beyond the 

 column; the subradials and first radials bear nodes or spines. The 

 rays divide on the third radial, and each division has three supra- 

 radials below the free arm-plates. In the typical species of this 

 genus by Rcemer, there are shown about fifteen interradial plates 

 and several interbrachial plates. 



In the Hamilton group we have at least two species, which, pre- 

 serving the formula of Rhodocrinus, have nevertheless an unusual 

 form for species of that genus, and approach the Acanthocrinus in 

 some of the more important features. I have therefore referred them, 

 for the present at least, to that genus or subgenus of Rhodocrinus. 

 In the same association we find a single globose form of Rhodocrinus, 

 with the arms in pairs surrounding the low dome. 



RHODOCRINUS (ACA.NTHOCRINUS) NODULOSUS ( n. s.). 



Body short, turbinate : height and greatest width about equal. Basal 

 plates pentangular, well developed, and separating the subradial 

 plates from the column-area. First radial plates pentagonal, or 

 sometimes with one of the lower angles truncate, giving an ir- 

 regular hexagonal form. Second radials hexagonal, wider than 

 high. Third radials pentagonal, or sometimes unequally hexago- 

 nal. The rays bifurcate, and have three or four simple plates in 

 each of the secondary radial series; above which, they become a 

 double series of pentagonal arm-plates. Arms bifurcating, be- 

 coming free at the fifth, sixth, or seventh range of plates above 

 the supraradial series, and again bifurcating a second and a third 

 (and perhaps a fourth) time; the bifurcations widely divergent. 

 If the rays are equal, the entire animal had at least forty arms. 



Interradial series consisting of fifteen or more plates, the first one 

 much larger than either of the others. Interbrachial series con- 

 sisting of about twelve plates. Column, at the base of the body, 

 large and round, with a pentangular cavity. 



Surface of the subradial and first interradial plates distinctly no- 



