tS9 PALAEONTOLOGY OF NEW- YORK. 



Pleurocystites ( Billings). Body inequilateral : basal plates six; one side com- 

 posed of lai^e plates, the other of small plates. Apicial range bearing two 

 arms. 



There appears to be some analogy between this genus and Anomaloq/stites. 



Several species : Lower Silurian. 



Malocystites ( Billings). Allied to Cryptocrinus. Basal plates three, with several 

 ranges of superior plates. 

 Lower Silurian. 



Anomalocystites ( Hall, p. 132). 



A. comuttu, A. disparilis : Upper Silurian. 



Agelacrtnus ( Vanuxem, 1842 ; Forbes, 1848). Mr. Forbes describes the Agela- 

 crinus as a many-plated body, having fine serpentine grooves radiating from 

 the mouth, in which lie the appressed arms. Ovarian pyramid in one of the 

 spaces between the arms. 

 A. hamiltonensis, A. hichianus : Devonian and Lower Silurian. 



Hemicystites ( Hall ). Body flattened, composed of imbricating scale-like plates : 

 five double ranges of elevated plates proceed from the centre towards the 

 margins, in the broadest space between which is placed the ovarian aperture. 

 Attached to other bodies. 

 This genus has been usually referred to Agelacrinus, but it does not correspond with that 

 genua as described by Forbes. Other species may perhaps show that the Lower Silurian, 

 Upper Silurian, and Devonian forms can be united in a single genus. 

 H. parasiticus. 



Hetebocystites ( Hall ). Basal plates four ; second range ten, with intercalated 

 smaller plates, and, above this, numerous smaller plates. 



The relations of this fossil have not been fully determined ; but from the irregularity of 

 its plates, it does not appear referable to the Crinoideae. 



H. armatus : Upper Silurian. 



