MUSEUM OF COMPARATIVE ZOOLOGY. 231 



corners of mouth-slits 2.2 : 2.2. Mouth-shields oval, with outer end cut off ; 

 length to breadth 1.2 : .8. Side mouth-shields broad and thick, -widely 

 touching within; they directly join the neighboring side mouth-shields; a 

 continuous ring is thus formed, and the usual rudimentary under arm-plates 

 are not interposed. Under arm-plates squarish with clearly rounded outer 

 corners ; length to breadth (2d plate) 1 : . 7. Side arm-plates only slightly 

 prominent. Upper arm-plates much broader than long, four-sided, bounded 

 without by a gentle curve, within by a shorter and re-entering curve, and on 

 the sides by straight converging lines; length to breadth (2d plate) .7 : 1.8. 

 ])i>k flat, but soft and a little wrinkled ; pretty evenly beset above with 

 minute, short, tapering spines, the longest about .2 mm. : below, a triangular 

 patch of similar spines. Radial shields long, narrow, pointed within ; di- 

 verging and completely separated : length to breadth 2.8 : .G. Under the 

 spines, the scaling of the disk is obscurely visible, especially between each 

 pair of radial shields. Arm-spines short, cylindrical, tapering; the lowest 

 usually longest : on the first four or five joints outside disk, usually four ; on 

 all beyond, only three: lengths to that of an upper arm-plate .6, .7, .8 : .7. 

 Tentacle-scales two (on first joint only one), small, not over one third as 

 long as an under arm-plate, and disposed at right angles to each other. 

 Color, in alcohol, pale gray. A young one with a disk of 4 mm. had the 

 primary plates in the centre of the disk, naked ; and often only three mouth- 

 papilla) on a side. 



I deem it best to leave this species under its present name, although it dif- 

 fers from Ophiophragmus echinatus Ljn. as follows : 0. longipeda has no 

 spines on radial shields, which also are wholly separated ; mouth-shields 

 oval and not four-sided ; four mouth-papilla? on each side : three arm-spines, 

 except on a few first joints. Vide Ljn. Oph. Yiven., p. 316. 



Philippines ; C. Semper. 



Ophiopsammium * gen. nov. 



Teeth : tooth-papilla) numerous and arranged in a vertical, oval clump, 

 as in Ophiotlirix. Xo mouth-papillae. Disk and arms naked below, but 

 closely granulated above. Arm-spines stout and thorny, mounted on a crest- 

 like side arm-plate, as in Ophiotlirix. Tentacles long, covered with papilla?, 

 and issuing,, not from the under surface, but from the side of the arm. 



This genus is nearest Ophiothela, but differs in having the whole upper 

 surface closely granulated, as also in the side arm-plates. 



* 6&IS, a snake; ^a^jj-iov , a granule. 



