1869.] MEEK AND WORTHEN — ON PALEOZOIC CRINOIDEA. 447 



in/uhdibulum), attached to oue side by its aperture, between the 

 arms of the Criaoid, and often so as to cover the single lateral 

 opening in the vault of the same.* From the direction of the 

 slight curve of the apex of the Platyceras, it is also evident that 

 it is always placed in such a manner, with relation to the Crinoid, 

 that the anterior side of the Mollusc was directed upward, when 

 the vault of the Crinoid was turned in that direction.-}- A species 

 of Goniasteroidocrinus ((r tuberosus, Lyon and Casseday), found 

 at the same locality, also has frequently a Platyceras attached to 

 the top of its nearly flat vault, so as to cover the only opening in 

 the same. It is worthy of note, however, that it is always 

 another, sub-spiral. Platyceras (very similar to P. cequilaterum), 

 that we find attached to this Crinoid, so that here at least, it 

 would seem that each of these two Crinoids has its own particular 

 species of Platyceras. 



* We at one time thought these shells attached to the side of this 

 Plattjcrinus, to be out of reach of the opening, or supposed mouth, 

 because we had not seen specimens showing the position of the opening 

 in this species, and had supposed, fi"om its similarity to Platycrinus 

 granuJattis, Miller, and other species without a lateral opening, that 

 such was also the case with this. We have since seen specimens, 

 however, showing that is has a lateral opening, and therefore beU)ngs to 

 the group Pleurocrinus, to that it is probable these shells often cover 

 this opening. 



tProf. Eichard Owen has noticed, in his Report on the Geological 

 Survey of Indiana, p. 364 (1862), the frequent occurence of a Platyceras 

 attached to this same Platycrinus, at this locality, and proposed to name 

 the Platyceras, P. pabulocrinus, from the supposition that it formed the 

 chief food of these Crinoids. It is probable that the Platyceras for 

 which he proposed this name, is the same we named P. i)ifiindihulum, 

 but as he gave no description of the species, and but an imperfect figure, 

 we cai not speak positively as to its identity. Prof. Hall has also 

 proposed the name of P. subrectum for this Crawfordsville Platyceras, 

 but he had previously used the same name for a very different, New 

 York, Devonian species of this genus. 



Prof. TanUell and Dr. Sbumard have also figured in their paper 

 entitled "Contributions to the Geology of Kentucky," a specimen of 

 Acrocrinus, with a very similar Platyceras apparently attached to its 

 vault. 



Amongst all the numerous Crinoids fouud at Burhngtou, Iowa, we 

 are aware of but a single instance of one being found with a Platyceras 

 attached, and that is a specimen of Actitiocrinus ventricosus in Mr. 

 Wachsmuth's collection, which has a crushed shell of a Platyceras 

 connected with its vault. 



