74 



POLYGYRA. 



P. implicata (Beck) Mart, iii, 



[133. 



P. oppilata Morel, iii, 133. 

 P. dysoni Shuttl., iii, 132. 



dorfeuilliana Pfr. not Lea. 

 P. chiapensis Pfr., iii, 138. 

 P. mooreana W. G. B., iii, 135. 



v. tholus W. G. B., iii, J35. 

 P. yucatanea Morel., iii, 146. 



v. helictomphala Pfr., iii, 130. 

 P. plagioglossa Pfr., iii, 133. 

 P. dissecta v. Mart., viii, 151. 

 P. couloni Shuttl., iii, 134. 

 P. bicruris Pfr., iii, 136. 

 P. richardsoni v. Mart., viii, 151. 



P. ventrosula Pfr., iii, 136. 



v. hindsii Pfr., iii, 136. 

 P. texasiana Moric., iii, 135. 



tamaulipasensis Lea. 



tridonia Beck. 



P. triodontoides Bid., iii, 135. 

 P. behri Gabb., iii, 134. 

 P. ariadn^ Pfr., iii, 132. 



couchiana Lea. 

 P. acutedentata W. G. B., iii, 



loisa W. G. B., iii, 134. [134. 



quinquedentata F. & C. 



v. unguifera Mouss., iii, 132. 

 P. anilis Gabb., iii, 130. 

 P. hippocrepis Pfr., iii, 134. 



P. johannis Poey, iii, 130. 



notata Poey. 



Section Triodopsis Rafinesque. 



Triodopsis plus Mesodon of authors. 



Shell varying from depressed to globose-conoidal, umbilicate or 

 imperforate ; surface generally striated ; whorls 5-6, the last wider, 

 more or less deflexed in front. Aperture lunate, typically obstructed 

 by three teeth, two on the lip, one on the parietal wall ; but any or 

 all of the teeth often absent. Type P. tridentala Say, pi. 30, fig. 8 

 (see also pi. 30, figs. 9, 10, P. appressa; pi. 30, figs. 13, 14, P. albo- 

 labris var. maritime^, pi. 30, figs. 17, 18, P. sayi}. 



Jaw sculptured with numerous moderately spaced ribs (pi. 30, fig- 

 19, P. sayi; pi. 30, fig. 21, P. kiawaensis; pi. 21, fig. 11, P. 

 albolabris). 



Radula having (1) ectocones with cutting-points developed on 

 central lateral and marginal teeth, as in P. tridentata, pi. 30, fig. 11,. 

 and P. albolabris, pi. 30, fig. 16, or (2) no side cusps or cutting- 

 points whatever on any of the teeth, as in P. clausa, pi. 30, fig. 15. 



Genital system as described for the genus (pi. 30, fig. 12, P. 

 inflecta; pi. 30, fig. 20, P. clausa ; pi. 21, figs. 12-16, P. albolabris^). 

 In P. albolabris Say (pi. 21, figs. 12-16) the lower third of the penis 



