228 Mr. F. M'Coy on the Fossil Botany and Zoology 



Ampleocus arundinaceus (Lonsd.). 



Common in the gray limestone of Curradulla or Limestone 

 Creek, N. S. Wales. 



CRINOIDEA. 



Tribrachyocrinus (M'Coy), new genus. 

 Gen. Char. Cup globose; pelvis (or dorso-central plate) large, 

 saucer-shaped, pentagonal, tripartite ; first costals (or first row 

 of perisomic plates) five, one pentagonal, three hexagonal and 

 one (?) heptagonal ; one of the hexagonal costals is truncate 

 above and supports one pentagonal interscapular plate; between 

 these and the heptagonal costal is situated one large, round- 

 ish, pentagonal, intercostal plate ; in the re-entering angle 

 between this latter and the summit of the heptagonal costal is 

 an obscurely hexagonal plate, analogous to a second costal. 

 Scapulae (or ray-bearing plates) three, rhomboidal or obscurely 

 pentagonal, upper margin rounded, lower margin pointed; 

 two of those in the re-entering angles between the first costals 

 and one in the angle between the intercostal plate and the 

 second costal. Interscapular plates three, shield-shaped, pen- 

 tagonal ; upper margin broad, straight, truncate, with the two 

 upper lateral angles horizontally extended into short angular 

 processes. 



The singular Crinoid for which I propose this genus is very 

 differently constructed from any other of the generic groups with 

 which I am acquainted. The cup is not symmetrical in form, 

 like that of other Crinoids, but is as it were humped on one side 

 by the interpolation of the large irregular intercostal (marked h 

 in the diagram) and the second costal (i). The only specimen 

 found is slightly crushed laterally, so as to render this inequality 

 of the sides very remarkable. The arm-bearing plates or scapula?, 

 which are so generally five in the other genera, are only three in 

 the present animal, forming a strong peculiarity which it shares 

 only with the genus Triacrinus of Count Minister (Beitrage zur 

 Petrefactenkunde), a little Crinoid of the Eifel differing in every 

 other respect from the Australian form. The general disposition 

 of the plates is most analogous to that of Poteriocrinus, from 

 which it differs in the number of the scapulae and every point of 

 detail. I am as yet only acquainted with one species of the ge- 

 nus, which it is not possible therefore to characterize specifically : 

 I have dedicated it to the Rev. W. B. Clark, to whose zeal we owe 

 the specimens described in this paper. 



Tribrachyocrinus Clarkii (M'Coy). PI. XII. fig .2. 

 The surface is smooth, with the exception of a few irregular 

 radiating plicae at the margin of some of the plates, which seem 



