(i) 64 Palasontologia Sinica Ser. B 



This fragment too shows no longitudinal lines, but in some of the interspaces 

 occur very faint indications of concentric lines. The specimen appears to represent the 

 filling of the living chamber, as a longitudinal section shows a total absence of septa. 



A still larger specimen, which is a partly crushed and incompletely exposed shell, 

 has a diameter of about 13.5 mm. and is characterized by abrupt annulations, the centers 

 of which range from 4.5 to 4.8 mm. apart. The annulations themselves have a thickness 

 of about 1 mm. ; tlie summit is rounded, and the interspaces are very nearly flat in some 

 parts, though tlicy show a concavit}' in otliers. Ko longitudinal sculpture is shown, but 

 there is again a faint indication of fine concentric lines in the interspaces. 



Only a few septa are indicated, their position corresponding apparently to the 

 annulations. Their concavity is about equal to half the distance between the annulations. 

 Siphuncle slightly excentric, large, its diameter being about 'l.b mm. where the diameter 

 of the shell is about 13.5 mm. 



Another specimen of this type (Plate VI, fig. 3) has tlie annulations slightly 

 oblique, l»ut sharply elevated, compressed and separated ly deep flat interspaces. The 

 distance Ix'tweon five annulations (including 4 interspaces) is 24 mm. the width of the 

 annulations Ijeing a little over 1 mm. at the base but only about half that at the top. 

 The diameter of this fragment is approximately 14 mm. and it appears to be slightly 

 curved. 



A still larger fragment apparently a part of the same individual as the preceding 

 (Plate VI, fig. o) shows annulations s.5 mm. apart, their thickness l>eing nearly 2 mm. 

 at the base, and their height al»out the same. This specimen shows fine sharp concentric 

 stri;e somewhat narrower than tlie interspaces lietween them, covering the entire shell, 

 including the annulations (Plate \1, fig. 4). There are about five of these striae in 1 

 mm. The diameter of this fragment was probably l^'tween 18 and 20 mm. Siphuncle 

 unknown. 



The last three specimens described differ rather strongly from the fragments 

 illustrated in figs. 1 and 2 of Plate VI especially in their narrow compressed and high 

 annulations^ and the very broad and nearly flat interspaces. It is quite possible that two 

 species are represented, but the material is too incomplete to warrant such a separation, 

 especially as the internal characters are not ascertainable. 



The generic position of this shell is in doubt. The entire absence of longitudinal 

 sculpture except in the very young stages, \\'Ould suggest that it belongs to the genus 

 Protocycloceras of Hyatt. The faijitness of the longitudinal sculpture on the young, 

 however, together with the pronounced character of the annulations, and further the 



