164 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



noticeable. Moreover they are so fragile they might easily be broken 

 off by rough handling, so that their absence would not prove that 

 a given specimen did not belong to this species. The interbrachial 

 scaling, arm plates and spines, oral shields and adoral plates are, 

 however, reliable specific characters. 



AMPHIODIA STRONGYLOPLAX, new species.o 



Disk 5i mm. in diameter; arms about 50 mm. long. Disk deeply 

 notched in interradii, covered bv a coat of numerous irregular 



/ o 



plates, without definite arrangement. Radial shields somewhat 

 curved, long and narrow^, rather broadly in contact distally, but 

 well separated within. Upper arm plates more or less rounded, 

 little wider than long, scarcely in contact even at base of arm, though 

 the side arm plates hardly meet between them. Interbrachial spaces 

 below, practically naked, though there are numerous white granules 

 of lime scattered about on the surface. Genital slits very large. 

 Oral shields large, pointed within, rounded laterally, truncate dis- 



FlG. 71. AMPHIOI;IA STRONGYLOPLAX. X 9. a, FROM ABOVE; 6, FROM BELOW; C, SIDE VIEW OF THREE 



JOINTS NEAR DISK. 



tally, about as long as wide. Adoral plates large, scarcely meeting 

 within, much wider at their outer ends. Oral papillae three, some- 

 times four, on a side. One at apex of jaw is thick and rounded; the 

 second is small and pointed; the third is large and bluntly pointed; 

 the fourth, if present, is very small. The scale of first oral tentacle 

 pore is visible between the first and second papillae. First under 

 arm plate very small, narrower distally than within; succeeding 

 plates tetragonal, with rounded corners, longer than wide, broadly 

 in contact. Side arm plates moderate, each with five arm spines, 

 of which the lowest is the longest and exceeds the joint. Tentacle 

 pores large, each with a single, minute scale. Color (dried from 

 alcohol), disk grayish, arms very light brownish; radial shields and 

 arm plates with an orange-brown tint. 



oc, signifying round, and ^Aaf, signifying plate, in reference to the rounded 

 upper arm plates. 



