292 bulletin: museltm of comparative zoology. 



arm-plates, much wider than long, hexagonal wdth slightly rounded 

 corners, more or less broadly in contact. Interbrachial areas below, 

 completely and abruptly naked; the contrast with the coarser, 

 marginal scales of the disk being very marked. Oral shields large, 

 rounded, triangular, fully as wide as long. Adoral plates very nar- 

 row, scarcely or not meeting within. Oral plates relatively large and 

 a little swollen. Oral papillae four or only three on each side, and in 

 addition the first oral tentacle-scale, which is very conspicuous, is 

 pushed down almost in line with the oral papillae between the thick, 

 block-like proximal one and the more scale-like ones which follow; 

 the tw'o distalmost are borne on the adoral plate but the outer one is 

 very small and is often imperfect or wanting. First under arm-plate 

 very small, squarish, thick; succeeding plates, longer than wide, with 

 distal notch and proximal, rounded angle. Side arm-plates small, 

 each with three sharp, slender spines, of which the middle one is 

 slightly the largest and about equals the arm-segment in length. 

 Tentacle-scales two, very small, particularly the one on the under 

 arm-plate. Color, in life and as preserved, disk very pale gray or 

 silvery; arms white with a brown tinge near base; many upper arm- 

 plates more or less dusky purple of a light shade, nearly always with 

 a white spot at center; these darker plates are very irregularly scat- 

 tered, sometimes occurring singly but more often several (3-5) to- 

 gether; arm-spines, and oral surface of body and arms nearly white. 



This species is undoubtedly near to both A. ahdiius and A. tuinidus 

 but is readily distinguished from them by the much finer disk-scaling, 

 the perfectly naked interbrachial areas ventrally, the big, wide oral 

 shields and the slender, sharp arm-spines. In A. tumidus, the entire 

 mouth-frames are heavier than in A. coniortodes and the adoral plates 

 in particular are bigger and thicker. 



Amphioplus thrombodes, sp. nov. 



0poju/?w57jj = lumpy, in reference to the condition of the disk-seales. 



Plate 7, fig. 1, 2. 



Holotype — M. C. Z. 4,218 and a Paratype, M. C. Z. 4,219. Florida: 

 Key West, June, 1917, in sandy mud near a mangrove key in 1-2 ft. 

 of water, with two other species of Amphioplus. Carnegie Expedition. 

 H. L. Clark coll. 



