ASPIDODIADEMA TONSUIM. 99 



figured by de Meijere and Mortensen, and in addition two other varieties. 

 A very careful examination of a specimen from Station 5079 revealed no 

 less than seven easily distinguishable kinds. The pedicellarioe of this species 

 may therefore be grouped as follows : 



The slender tridenlate are fiiirly common all over the test. The valves 

 are about one millimeter long, with straight margins and rounded tips. The 

 length of the blade varies proportionally as well as actually, but these pedi- 

 cellarise are always easily recognized. 



The stoiit irideidate are often common, sometimes rare, and occasionally 

 wholly wanting. They occur mainly near the abactinal system. The 

 valves are comparatively short, usually under a millimeter long, but very 

 broad in proportion, the width about 80 per cent of the length. The mar- 

 gins are scarcely sinuate and the tip is blunt, sometimes truncate, sometimes 

 bent inward as a broad, flat tooth. The blade is nearly filled with a 

 calcareous network. 



The form b is very diffierent, and is very rare. The few specimens we 

 found were near the abactinal system. The valves (PI. 50, fig. S) are 

 rather more than a millimeter long, about half as wide, rather flat, and 

 broadly rounded at the tip. There is a well-developed network in the 

 blade and no articular loop. 



The/(9?';?i c, which is quite rare and frequently wanting, is closely allied, 

 though we do not find intermediate stages. The valves (PI. 50, fig. 4) are 

 about .50 mm. long, with the blade about equal to the basal part. The tip 

 may be bluntly pointed (as in our figure) or more truncate (as shown by de 

 Meijere), while a small articular loop is usually present at the base. 



The ojihiceplialous pedicellarioe are not very common, and occur mainly on 

 the interambulacra. They have three small valves, each with an articular 

 loop, and are broadly rounded at the tip. 



The triphyllous pedicellariie are common everywhere. The valves are 

 rather slender, with round tips, as figured by de Meijere. 



The hroad triphyllous are rare, and are at once distinguished by the flat, 

 truncate, almost square-cut tips (PI. 50, fig. 5), which are twice as broad as 

 the base. We found none intermediate between these and the common form. 



The calcareous particles in the pedicels commonly have the ends drawn 

 out and imperforate as figured by de Meijere, but narrow, irregular, perfor- 

 ated plates also occur. The sphoeridia show no characteristic features. 

 This species was taken by the •' Albatross " at the following stations : 



