146 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



Plate 18. 



Fig. 1. Amphiura palmeri, under face. X". 



2. Ophioderma clypeata, upper (sLce. X1.6. 



3. Amphiura palmeri, upper face. X6. 



4. Ophioderma elaps, under face. X2.7. 



5. Amphiura rathbuni, upper face. X7. 



6. Ophioderma clypeata, under face. X2.7. 



7. Aviphiura rathbuni, under face. X7. 



8. Astrochema elongatum, side view of an arm near the base. X3. 



