Geological Society. 471 



A single specimen in the Hunterian collection affords the type of 

 a third genus. 



(3.) Psaliodus (\pa\ls forfex, and ohovs dens). 



Upper jaw } Two maxillary plates in the lower jaw. Lower max- 

 illary like Chimcera, but without a triturating tubercle ; structure 

 homogeneous ; outer surface reticulated. Sp. Psaliodus compressus, 

 Egerton. It is supposed to be from the London clay. 



A paper was read " On the Locomotive and Non-locomotive pow- 

 ers of the Family Crinoidea." By J. C. Pearce, Esq., F.G.S. 



The author is induced, from an examination of the various modes 

 of attachment among the Crinoidea, to separate those animals into 

 two great groups, the Non-locomotive and the Locomotive. The 

 former, when once attached to any solid substance by their base or 

 foot, were immoveably fixed ; the latter possessed the power of grasp- 

 ing with the foot any substance, and again relaxing their hold at 

 pleasure. The non-locomotive Crinoidea he subdivides into solid- 

 footed and root-footed. In the solid-footed the foot is formed like 

 an irregular cone with the base downwards, and is composed of suc- 

 cessive laminae, which envelope the inferior part of the column and 

 increase in number as the animal advances in age. This base or 

 foot is generally found firmly adhering to the rock in the fossil state, 

 although specimens are sometimes found detached which appears to 

 have been caused by violence during life. The columns of all the 

 species which Mr. Pearce has examined are very short and destitute 

 of side-arms. He enumerates Encrinites moniliformis from the Mus- 

 chelkalk, Apiocrinites rotundus from the Bradford clay, and Cyatho- 

 crinites tuherculatus from the Dudley limestone, as examples of this 

 group. In the non-locomotive root-footed Crinoids the base is com- 

 posed of many root-like branches, radiating in a more or less hori- 

 zontal or downward direction from the lower part of the column, 

 each branch bifurcating several times in an irregular manner. The 

 branches are perforated by a central foramen, and appear to be com- 

 posed in individuals of all ages, of a solid calcareous substance in- 

 capable of motion. 



Mr. Pearce divides his locomotive Crinoidea into two sections. 

 Branch-footed and Sucker-footed. The branch-footed are charac- 

 terised by the organ of attachment, or foot, being composed of a 

 number of jointed branches, in some species simple, in others bifur- 

 cating, or dividing in an irregular manner, and generally terminating 

 in a minute blunt point. Each joint has a central foramen, and is 

 articulated by alternate radiating ridges and grooves, admitting of 

 the greatest degree of flexibility, forming an organ which the author 

 regards as well adapted to crawl along the bottom of the ocean, or 

 to steady the animal against the motion of the water. The columns 

 of this group are generally furnished with side-arms, extending to a 

 greater or less distance from the foot, and sometimes the whole 

 length of the column. Examples are, Apiocrinites ellipticus from the 

 chalk, Pentacrinus Briareus from the lias, Actinocrinites tessellatus, 

 Platycrinites gigas, and several undetermined species from the moun- 



