KXI'LANATION OF PLATE XXXVII. 



ClilOCERAS JACKII, I'.lll.jil. 



Fig. 1. Lateral view of the earlier whorls, partly testiferous, displaying the 

 semi-open coil and swollen tuberculate costae ; the costs in general 

 are gently sigmoidal and at rare intervals bifurcate ; the secondary 

 cost;e are also more numerous than usual, and, like the primary, 



increase in thickness towards the venter. The three rows of 

 tubercles arc also well shown, the abdominal and supra-dorsal rows 

 in this instance continuir.tr as far as one another. 



,, 2. Similar view of another specimen, partly testiferous, and possibly 

 somewhat older than that represented in Fig. 1, with rugged and 

 large tubercles ; here there is usually the normal number of 

 secondary costaj. 



