OPHirEOIDEA FROM THE KOREAN SEAS. 



451 



tentacle. The tentacle-scale becomes microscopic towards the 

 seventeenth joint, and minute tentacles are seen thus far out. 



The first tentacle-opening, slightly curvilinear, has four broad, 

 but short, close, straight-edged tentacle-scales, two on cither side. 

 The next has a short ridge and a spiny scale on the side arm-plate, 

 and a raised rim on the lower arm-plate ; and the third has a small 

 scale on the side arm-plate alone. 



The upper arm-pktes near the disk are boss-like. There are 

 two small plates within the notch which are broader than long, 

 close and convex from side to side. The next plate is overlapped 

 slightly by the second, is boss-like and convex, strongly rounded 

 without, and the sides slope in towards the disk. The fourth 

 upper arm-plate is separated from the third by the side arm-plates, 

 and is irregularly heart-shaped and boss-like and convex, espe- 

 cially distally ; it forms about one half of the breadth of the 

 joint, the rest being made up by the expanded distal part of the 

 side-plates. The succeeding upper arm-plates diminish in size in 

 all directions, and become more angular ; and the last is seen on 

 the twelfth or thirteenth joint. 



The upper parts of the side arm-j)lates unite in long median 

 lines ; they are constricted within and expanded distally. Three 

 very short stumpy arm-spines are in a depression on the side of 

 the plate, close to the edges. The upper spine is the smallest, 

 and they are unequally distant. 



Locality. Korean Straits, 51 fathoms. Collected by Capt. St. 

 John, E.K 



Ljungman has established the genus Opliiothyreus in order 

 to separate one species, O. Goesi, Lj.,from Opliiomusium.Jjjmim 

 (see Stockholm (Efversigt af Kong. Yet. Forh. 1871, published in 

 1872, arg. 28, pp. 619, 620). This genus is characterized, amongst 

 other peculiarities, by papill£e, some fifteen in number, projecting 

 downward on the margin of the innermost arm-plate ( •' margine ad 

 scutellum brachiale intimum vergenti papillifero "). The inner- 

 most upper arm-plate, large and triangular, is divided into two 

 parts — the under arm-plates " inter sese taugentia," and the side 

 arm-plates " ad brachium medium versus primum inter sese 

 paullum tangentia." There are two squamiform ambulacral 

 papillae " ad ternas," and two minute arm-spines reaching, like the 

 papillae, to the third plate only. 



This genus has Ophiomusoid characters, especially in the ab- 

 sence of the tentacles from the distal arm-divisions ; but the 



33* 



