REPORT ON THE OPHIUROIDEA. 



355 



it had been lifted and turned outwards, so as to expose its under surface. The soft 

 tissues are removed, though, in some cases, the muscles between the arm bones have 

 been left. Besides this there usually are given views of the outer and inner faces of an 

 arm bone, from near the disk ; and sometimes a view in profile, or from above, or below. 

 The same notation is everywhere used as follows : — 



a, INIoutli shield. 



c, Jaw. 



d, Mouth papillae ; d', tooth papillse ; d", teeth. 



e, Jaw plate. 



/, jSIouth frame, /', /", upper and lower hinges 



joining a mouth frame to its neighbour. 

 g, Central primary plate; g' brachial primary 



plate. 

 li, Under arm plate. 

 i, Side arm plate. 

 j, Upper arm plate. 

 I, Radial shield. 

 n, Genital scale. 

 0, Genital plate. 

 p, Arm spines. 



r, tentacle socket ; r',r", sockets of first and second mouth 



tentacles. 

 s, Marginal scales or disk plates. 

 t, Lower arm canal ; t' upper arm canal. 

 u, Circular nerve ring canal. 



y, Peristomial plate; v',angle piece (first under arm plate?). 

 ?ff, Lower muscle field of arm bone ; w", upper muscle 



field ; w', the arm bone as a whole. 

 S, Ovarial bursa. 



1, Articulating umbo on the inner face of an arm bone. 



2, Articulating knobs on the inner face of an arm bone. 



3, Hole to receive the articulating peg of the outer face. 



4, Shoulder on the outer face to receive the umbo. 



5, Holes in the outer face to receive the knobs. 



6, Articulating peg. 



For a more detailed treatment of the plates, see the descriptions of the genera 

 referred to. 



20 



T • 



20 



1 • 



Ophiura elaps (?), Ltk., f . Expedition of United States steamer " Blake." 

 ,, „ J. Outer face of an arm bone. 



,, „ f . Inner face of an arm bone. 



OpMopcBpale goesiana, Ljn., Y. The peculiar elongated arm bones (w'). 



Outer face of an arm bone. Its unusual height 



and complex outlines will be noticed. 

 Inner face of an arm bone. 

 OpMolep>is cincta, Mllll & Tr., f. 



Outer face of an arm bone. 

 Inner face of an arm bone. 

 Ophiophcus imbricatus, Ljm., f. 



Outer face of an arm bone. 

 Inner face of an arm bone. 

 Ophiozona impressa, Lym., f . Outer face of an arm bone. 



18 

 T • 



L8 

 1 • 



12 

 T • 



12 

 1 • 



1J5 

 1 • 



Y^. Inner face of an arm bone. The umbo is very 

 large and the bone wide. 



