Agelacrinidae and Lepadocystinae 
405 
right hand side ^of the anal pyramid, and similar features are 
presented by the specimen of Agelacrinus holhrooki which was 
figured by Clarke {New Agelacrinites, p. 189, Fig. 2, 1901 ; see also 
plate I, Fig. 1C, of this Bulletin) , in which the small plates also are 
specially numerous along the upper right hand margin of the anal 
pyramid, if the specimen be oriented so as to direct the proximal 
part of the right ray (No. 4) toward the top. 
In specimens of Agelacrinus cincinnatiensis in which the supple- 
mentary small plates along the upper right hand margin of the 
anal pyramid are either absent or few, the distal part of the right 
posterior ray (No. 5) 'usually is parallel to the peripheral ring and 
terminates opposite the middle of the anal pyramid. In speci- 
mens in which the supplementary small plates are numerous 
along the upper right hand margin of the pyramid, for example, in 
specimen No. 13266-1-b, cited above, the tip of the right posterior 
ray curves distinctly, at the very extremity, away from the periph- 
eral ring, toward the anal pyramid. In typical Agelacrinus 
holhrooki, also with numerous supplementary plates along the 
upper right hand margin of the pyramid, the tip of the right 
posterior ray curves still more strongly and terminates above the 
level of the anal pyramid (plate I, Fig. ID), the specimen being 
oriented, as before, so as to direct the proximal part of the right 
ray (No. 4) toward the top. In this case, also, it will be noted that 
a few smaller sized plates occur on the inner or concave sides of 
the distal parts of some of the other rays of Agelacrinus holhrooki, 
possibly owing to crowding. 
In Agelacrinus pileus, no supplementary smaller plates were 
noticed along the margin of the anal pyramid, and no evidence is 
here suggested of any cause for the reversal of curvature of the 
right posterior ray, from contrasolar to solar. 
6. Reversal of Curvature in Streptaster 
No cause of the reversal of curvature of the right posterior ray 
of Streptaster reversata (plate IV, Fig. 3), described in this paper, 
is suggested by any detail of structure noted so far. The two 
species of this genus, previously described, have all the rays 
curved in a contrasolar direction. 
