ECHINODERMATA OF NEW ENGLAND. 



65 



Opkfuridce. 



Disk circular and togumentose above, with or without 

 radial plates. No anus. Madreporic body small, or 

 wanting. Arms simple, with aboral, lateral and ventral 

 plates. Ambulacra! plates hidden under the ventral. 

 Blood system and nerves covered by ventral plates ; feet 

 in single row at edge of the ventral plates, without suckers 

 or ampullae. Motion by jerks. Hermaphrodite or bisex- 

 ual. Young has a free pluteus, or adult viviparous. 

 Genital slits large. 



Ophiop holts. Disk with small spines. Teeth. No 

 teeth papillae. Arm-spines flat, stout, arranged on the 

 side plates. Color 

 generally brownish- 

 red. Primary plates 

 in brachial and in- 

 terbrachial regions. 

 Young, pluteus. 



O. aculeata. 

 QpMoglypha. Di^k 

 with crowded, nak- 

 ed, distorted scales. 

 Radial shields swol- 

 len. Arm-spines few 

 (three). Tentacle 

 scales numerous. 

 Color gray with light OPHIOPHOLIS. 



bands on the arms, also yellowish. Probably viviparous. 



0. Sarsii. 



Amphiura. Disk small, delicate, with naked overhanging 

 scales. Arms slender. Arm-spines short. Arms four and 

 one-half times the diameter of body. Color brown. Vi- 

 viparous. A - squamata. 



ESSEX INST. BULLETIN, VOL. XXIII 5 



