112 Cincinnati Society of Natural History. 



A. incurvus — Height of bod}-, on the posterior side, 0.67 inch, and 

 on the anterior 0.43 inch; greatest breadth 0,92 inch; thickness of 

 column at its connection with the body 0.34 inch. 



A. caponiformis. — Height of body, on the posterior side, 0.67 inch, 

 and on the anterior 0.35 inch; greatest breadth 1.65 inches; thickness 

 of column at its connection with the body 0.34 inch. 



The width of the right anterior first radial in A. caponiformis is 9- 

 lOths inch, in A. incurvus it is 5-lOths inch, while the height of the 

 former is 36-lOOths, and the latter 28100ths. Other plates show the 

 same difference between the relative proportions of width and height 

 in the two species. 



The five basal plates in A. caponiformis form a pentagon of al- 

 most equal sides, while the six basal plates in A. incurvus., form 

 arcuate faces to a sub-pentagonal figure. The cup of the latter is 

 subangular in the direction of the arms, a feature not possessed by the 

 former. These and many other minor differences may be pointed out, 



I know of no species among the palaeozoic crinoids, which is held to 

 include forms so distinct as these, while subgenera are formed upon 

 peculiarities of much less importance. 



A word ought, perhaps, to be said upon the question, whether the 

 specimen described and illustrated, in the Ohio Palaeontology, is 

 specifically' the same as the one described in the Illinois Geo. Sur,, 

 upon »vhich the Anomalocrinus inciirvus was established. I have 

 before said, that the diagrammatical structure, in the 111. Geo. Sur. is 

 erroneous, and where such a poor representation is made, we may fairly 

 attribute it to the imperfection of the specimen. The specimen may 

 have possessed six basal plates and yet only shown five, on account 

 of the imperfect preservation or the anchylosing of the plates. The 

 general outline of the specimen as represented on the plate, is the same 

 as that represented in the Ohio Palaeontology. I, therefore, conclude, 

 that the specimens represented in the Illinois and Ohio Surveys both 

 belong to Anomalocrinus incurvus. 



I may add that the specimen of Anomalocrinus caponiformis, here 

 illustrated and defined, is the only one I have ever seen, and it is, 

 therefore, extremely rare. It is quite true, too, that Anomalocrinus 

 incurvus is very rare, and that but few collectors have a moderately 

 good specimen of it. 



TuicnopnYCus VENOfeUM, n. sp. 



Plate IX., fig. 5, showing diagonal lines, natural size. 



fig. 5a, showing the irregularity of the elevated lines, natural size. 



This plant, as known to me, consists of a half cylindrical stem. 



