Remarlrs ♦ - jsnto Doming-ian speciniens of this species reach an 

 enormous size, "being as much as 115 mm. hip-h 8az' 100 Mn. vzide, 

 r;ith t'ne primary rt dials not prominent and hearing a few spines, 

 the whole surfsce slightly scahrous. j?orms from other localities, 

 incln.din.?? Borrden, are never of such an iaiposing size and oerhaos 

 should be considered a distinct variety. The Bov;den form referred 

 to this species is characterise'^ hy its moderately inflate"!, round- 

 el form, relatively few, lo7/, narrow, spinose orimary ribs with 

 intervening non-ST)inose secondaries and longitudinal striae on 

 and between the secondaries. Speci'^nens from the type locality have 

 the primaries narrower and less spinose, but a'onarently these char- 

 acters are susceptible to variation, for specimens from other .Int- 

 illean localities that are com"oarable in other features to those 

 from Bowden have the sculT^tnre of the S—nto DominglaJi form, the 

 ribs beijig as narrow or even narrov;er. The advisibility of includ- 

 ing the Tampa sile^ form is doubtfiil since it is narrower, more 

 inflated, witt- « v-id.er ©nd shorter cardinal area. 



A very closely related form, _3. chipolan^rs Dcll,(l) occiirs 



(1). loo. cit., 010. '^"':-7o9, 1338; loc. cit., n. 1^5, b1. 1^, 

 fi5-. 1, 1915. 



in the Ohipola and Oak Grove faunas; it is more oval and inflated, 

 with more numerous spinose ribs ai':d concentric striations on the 



