Mr. F. B. Meek on the Genus Lichenocrinus. 341 



XLV. — Remarks on the Genus Lichenocrinus. 

 By F. B. Meek*. 

 Perhaps of all the remarkable types of that protean order of 

 animals known as the Crinoidea^ there are few more curious 

 and interesting forms (if really the body of a crinoid) than 

 that for which Prof. Hall proposed the name of Lichenocrinus. 

 Having recently had an opportunity of examining an extensive 

 series of specimens belonging to both of the known species of 

 this type, in the collections of Mr. C. B. Dyer and other gen- 

 tlemen of Cincinnati, I propose to make a few remarks on the 

 same, that may be of some interest to palseontologists, espe- 

 cially as this fossil is little known, and the specimens now 

 obtained afford the means of giving a more extended descrip- 

 tion of its characters than that already published. 



Prof. Hall's generic description of this crinoid reads as fol- 

 lows : — " Bodies parasitic on shells and other foreign sub- 

 stances. Form discoid or depressed-convex, with a proboscidi- 

 form appendage rising from the centre. Disk composed of an 

 indefinite number of polygonal plates, and apparently having 

 no distinct mode of arrangement. Proboscis perforate, and, 

 in the known species, formed of five ranges of short plates 

 alternating and interlocking at the margins." 



From the specimens now known, the following more ex- 

 tended description of this fossil may be given : — 



Discoid or depressed-plano-convex bodies, growing firmly 

 attached to shells, corals, trilobites, and other marine objects, 

 and entirely destitute of free or recumbent arms or pinnulee, 

 ambulacral openings, or pectinated rhombs. Free or convex 

 side concave in the central region, and composed of numerous 

 small, non-imbricating polygonal plates, without any definite 

 arrangement ; mesial depression provided with a. very long, 

 slender, perforated, flexible, column-like appendage, composed 

 of five longitudinal series of short, alternately interlocking 

 pieces. Attached side, when separated, presenting no sutures 

 or openings, but in some conditions showing numerous, di- 

 stinct, regularly arranged, radiating striae, corresponding to 

 radiating lamellse that occupy the whole internal cavity from 

 top to bottom. 



Among the more remarkable features of this fossil may be 

 mentioned its very curious system of radiating lamellas occu- 

 pying the whole internal cavity, and giving it, when the plates 

 of the upperside are removed so as to expose these lamellae in 

 place and attached to the adhering side, almost exactly the 

 appearance of the little fungioid coral Micrabacia. The entire 

 absence, so far as known, of free or recumbent arms or pin- 

 * From Silliman's American Journal, October 1871. 



