2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. yo 



inner sides they are seen as two tiny apposed hydrospire elevations. 

 Plates of the lower side very finely pitted, but it is not thought that 

 these pits bear pores going through the plates to the body cavity. 



Fig. I. — A, Stroinatocystitcs walcotfi, n. sp. The centrodorsal plate, and the 

 first circle of lo plates in outline, X 5- B, -S". zualcotti, n. sp. Some of the 

 plates of the upper side, showing the diplopore spiracles, as seen from their 

 inner surface, X 5- C, S. zvalcotti, n. sp. Part of an ambulacrum showing the 

 flooring plates, X 5- ^•'. distal, P , proximal end ; s. ridges of the side plates. 

 D, S, walcotii, n. sp. The animal in section, X 2. E, 6". pcntangularis Pom- 

 peckj. A restoration of the upper surface by F. A. Bather, somewhat en- 

 larged. As, anus ; O, peristomial plates, c. p., covering plates, j. p., side plates, 

 ia, interambulacrals. 



Ambulacra restricted to the upper side, straight and narrow, bounded 

 on either side by a column of about ii to 13 narrow elongate plates ; 

 ambulacral groove deep and seemingly floored by two columns of 

 elongate, narrow, and alternating flooring pieces ; the two columns 



