REPORT ON THE OPHIUROIDEA. 3(51 



Fig. 16. Ophiobyrsa rudis, Lym., f. The plastron-like genital plate (o) coming high on 



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

 («•) is peculiar, as is the large, closely-attached 

 peristomial plate (t?). 



,, 17. ,, ,. 1 1 °. Outer face of an arm bone. 



,, 18. ,, ,, 1 1 D . Inner face of an arm bone. 



PLATE XLIV. 



Fig. 1. Astroschema oligactes, Ltk., Y . 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 (i/) is very con- 

 spicuous. In simplicity and massiveness, 

 the skeleton has some likeness to that of 

 Hemieuryale. 

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



the true Astrophyton type. 4 is the hollow 

 corresponding to the articulating shoulder 

 among Ophiurans. 

 ,, 3. ,, ,, 1 £ > . Inner face of an arm bone. 1 is the modified 



umbo of the Ophiurans. 

 ,, 4. ,, ,, ij 5 . Arm plates of one joint, viewed diagonally; 



under arm plate (/;), side arm jilate (/), 

 tentacle holes (r), broken pieces corre- 

 sponding to upper arm plates (j). The 

 entire arrangement is like that found in 

 Ophiomyxa. 

 ,, 5. ,, ,, Y*. A joint, about three-fourths out on the arm, 



in profile. The granulated skin is slit to 

 show the side arm plate (i), 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. 



