REPORT ON THE OPHIUROIDEA. 361 



i'ig. 16. Ophiohy rsa rudis, Ijym.., ^. The plastron-like genital plate (o) coming high on 



the arm, having a horn-like scale soldered to it 

 ill) is peculiar, as is the large, closely-attached 

 peristomial plate {v). 



„ 17. ,, ,, \^. Outer face of an arm bone. 



,, 18. ,, „ \o_ Inner face of an arm bone. 



PLATE XLIV. 



Fig. 1. Astroschema oUgactes, Ltk., \^. A mouth angle, with its two neighbouring 



mouth frames (f), and one arm bone from 

 above. The massive radial shield (I) is 

 turned on one side, exposing the thick 

 genital plate (o) with its elementary scale 

 (n). The angle piece {if) is very con- 

 sj^icuous. In simplicity and massiveness, 

 the skeleton ha.s some likeness to that of 

 Hemieuryale. 

 „ 2. ,, „ \^. Outer face of an arm bone, with a joint of 



the true Aatroiihyton tj^e. 4 is the hollow 

 corresponding to the articulating shoulder 

 among Ophiurans. 

 ,, 3. ,, „ \''. Inner face of an arm bone. 1 is the modified 



umbo of the Ophiurans. 

 ,, 4. ,, J, \^. Arm j^lates of one joint, viewed diagonally; 



under arm plate (//), side arm plate (t), 

 tentacle holes {;•), broken pieces corre- 

 sponding to upper arm plates [j). The 

 entire arrangement is like that found in 

 Opliiomyxa. 

 „ 5. „ ,, ^f. A joint, about tlirce-fourths out on the arm, 



in profile. The granulated skin is slit to 

 show the side arm plate (/), carrying a 

 large tentacle scale (spine), and the pieces 

 above. From behind it protrudes the 

 tentacle (r). At this point there is no 

 under arm plate, or, at the most, a 



granule. 



