2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 9I 



are larger than the others, with broadly rounded outer edges and 

 with the outer portion somewhat swollen. The radial shields are 

 rounded triangular and are about twice as long as broad. The shields 

 of each pair are separated by a column of usually four plates, of 

 which the innermost is trapezoidal and much longer and broader 

 than the others. Interradially, the radial shields are separated by a 

 column of two or three more or less oblong plates. 



The six arms are i8 mm long and 1.8 mm wide at the base. They 

 are narrow, about 2.6 times the diameter of the disk in length, 

 and taper evenly from the base to the tip. Their bases are separated 

 by a distance of i.i mm, the interbrachial margins of the disk 

 being straight, so that the arms and the disk are rather abruptly 

 differentiated. 



The earliest upper arm plates are fan-shaped with broadly trun- 

 cated lateral angles ; they are about half again as broad as long and 

 are in contact by their proximal angles. After the sixth or seventh 

 they gradually become separated and reduced in size, so that at the 

 arm tip they are very small and are separated for about their own 

 length. In the earlier portion of the arm they are slightly swollen. 



The supplementary arm plates resemble those in Sigsbeia murrhina. 

 They decrease in size distally and at the arm tips are simply minute 

 plates attached to the lateral angles of the upper arm plates. 



The side arm plates are large, slightly swollen, and in contact 

 dorsally. 



The under arm plates resemble those in Sigsbem murrhina. 



The single tentacle scale is subcircular. 



On the second pore there is a single short and very broad arm 

 spine that resembles the tentacle scale. At the second, third, and 

 fourth pores there are two very short and broad spines, which are 

 only slightly, and sometimes not at all, longer than broad. From 

 this point onward the upper arm spine very slowly diminishes in 

 size, the lower remaining the same, until near the arm tip the upper 

 spine disappears, the lower concurrently becoming somewhat longer 

 and slightly recurved and acquiring several stout, glassy spinules 

 on the lower side of the tip. 



The jaws are triangular with the outer apex more or less blunted 

 and are about half again as long as broad at the base. 



There are three mouth papillae on each side, which form a con- 

 tinuous narrow line along the jaws. The first mouth papilla is the 

 longest and broadest and tapers somewhat distally. The second 

 mouth papilla is narrower, and the outermost is broader again, but 



