PLATYCRIND.E. PLATYCRINUS. 39 



Synonymes and References. 



Platycrlnus gigas.— Pliill. Geol. Yorlc. PI. III. fig. 22 and 23. 



Aust. Ann. ^ Mag. Nat. Hist. vol. 10, p. 100. 



Formation and Localities. 



Carboniferous limestone. — Colland ; and the Mcndip Hills. 



This species is not very extensively diffused through the limestone strata in which 

 it occurs, as but few specimens have hitherto been obtained ; and those few are so 

 imperfect that we are unable to offer any description of the rays, column or the more 

 delicate organs which forai such interesting features in the Crinoidea when obtained in 

 a more perfect state of preservation. 



The ^/^rts appears to have attained to a considerable size, and though we have met 

 with specimens of the P. trigintidactylus fully as large, yet the characters are so clearly 

 dissimilar that no mistake can occur when comparing the two species. The large 

 abdominal plates, and the slightly obtrusive mouth of the former, are alone sufficient to 

 distinguish it from the latter, with its elongated oral tube; besides the difference in the 

 form of the perisomic plates, and the excavations for the rays, are quite characteristic. 



Description of the Calcareous Frame Work. 



The Dorso-central Plates — Are somewhat contracted at the columnar point of 

 attachment ; which is small when compared with other species of Plattjcriiii. The 

 undulations for the reception of the perisomic plates are slightl}' orljicular. 



The Perisomic Plates — Are broad, and the excavations for the rays large, but not 

 deep, as in the P. trigintidactylus. These and the dorso-ccntral [jlate are quite smooth. 



The Meso-Plates — Are large and hexagonal, with a small tubercle in the centre 

 of each. 



The Abdominal Plates — Large, with a central tubercle. 



The Mouth. — Central, and not proboscidial. 



The Column and ravs unknown. 



