SYNTHETIC TYPE OF OPHIUBID. 75 



jaw; it projects downwards and outwards, and is in relation to 

 the tentacle-opening. The jaws are swollen just externally to the 

 very distinct jaw-plate. The true teeth are five in number 

 and the lowest is small and knobbed ; it aborts in some angles ; 

 the next is long, broad and concave orally ; and the others are 

 shorter, flat, and slightly rounded where free. There are no tooth- 

 papilla?, neither are there mouth-papillee on the sides of the jaws. 

 The first upper arm-plate is small, broader than long, widest 

 and curved distally, and narrower near the disk ; it has spinules on 

 it resembling those on the disk. The second plate is larger than 

 the first, is about as broad as long, is broadest distally, the edge 

 being curved outwards. The sides slope in towards the short 

 oral edge, and the whole plate is convex from side to side ; it has 

 a few spinules on it in some instances. There are several (five) small 

 accessory plates which are attached to the curved distal edge, and 

 each one carries a spinule. An accessory plate is also on each 

 side of this upper arm-plate near the proximal edge. The third 

 upper arm-plate is longer than broad and is narrowest proxi- 

 mally ; the accessory plates are in contact with its distal edge, 

 and there is a knob on each side near the proximal edge, 

 but it is not thorned. Three accessory plates are found in re- 

 lation to the next plate and to the eighth ; they are not fixed on 

 to the edges, for they separate readily. The side knobs are found 

 on these plates also, and usually there is a thorn on each. 



The first lower arm-plate is very small, rounded distally, and is 

 prolonged towards the mouth upwards, and it bounds part of the 

 wide space between the jaw-angles ; the second is much larger, 

 and is square with a slight re-entering aboral curve ; the outer 

 angles are rounded, and the inner are incurved for the passage of 

 the tentacle and the incoming of the side arm-plate. The next plates 

 are longer than broad, are broadest without, have a more or less 

 straight edge distally, and the oral edge is narrow and rounded ; 

 far out on the arm they are longer than broad. 



The side arm-plates are stout, long, tumid at the sides when 

 seen from above, and the spines project at right angles from them. 

 The plates encroach on the upper arm-plates, but do not meet 

 along the median line. On the lower surface of the arm they 

 form stout processes, which reach nearly, but not quite, to the 

 median line and form much of the surface. They form large 

 flaps on the sides of the arms, and their free and spined distal 

 edge projects outwards beyond the narrow proximal edge of the 

 plate beyond. 



6* 



