ACTINOCRINIDZ&. 587 
only one to which his description applies, is an Actinocrinus. The other was 
made by Austin in 1848 the type of Amphoracrinus, and is now known as 
Amphoracrinus Gilbertsoni (Miller) = Actinocrinus amphora Portlock, and 
Melocrinus amphora Goldfuss. 
Roemer and Hall confounded Amphoracrinus with Agaricocrinus, and Meek 
and Worthen at first with Dorycrinus, but afterwards accepted the genus in 
its present form. It differs from both genera essentially in the arm struc- 
ture, as well as in the form and position of the anus; and they have also 
uniformly a second anal plate. 
Amphoracrinus appears to be a somewhat aberrant form, and has quite 
frequently three plates above the anal piece. This, however, is found only 
among the American species, and only in A. diwvergens and A. vimunalis ; 
Amphoracrinus spinobrachiatus and the three English species always having 
the usual two plates. This might seem to indicate that the two former are 
generically distinct, and should be removed to the Batocrinide, if it were 
not for the fact that they also have occasionally but two plates above the 
anal, and that in their arm structure, as well as in other respects, they agree 
most closely — even more than A. spinobrachiatus — with the typical form 
from England, of which we have a most excellent specimen with arms, from 
Waterford, Ireland. To understand the case correctly, it is important to 
note that the middle plate over the anal, when it does occur, is compara- 
tively small and cuneate, often barely touching the anal plate ; and we think 
it not improbable that it really represents a plate of the second row, and is 
not a true homologue of the middle plate in the Batocrinide. On the other 
hand, we must remember that Amphoracrinus is one of the earliest represen- 
tatives of the Actinocrinide ; and it may be possible that it is a transition 
form, in which the Actinocrinoid structure has not been as yet persistently 
established. At any rate, we see no good reason for separating the two 
forms, even subgenerically. 
Worthen, in the Geol. Rep. of Illinois (Vol. VIII. p. 96, Plate 14, Fig. 8), 
described a specimen under the name of Amphoracrinus jerseyensis, Which is 
interesting as having but four arm-bearing rays, the free parts of the anterior 
ray evidently having been destroyed during the life of the animal, and the 
break closed by abnormal growth. The specimen is too imperfect for a cor- 
rect diagnosis, and we think it highly probable that it is an Agaricocrinus. 
