WOOD. PHYLOGEXY OF CERTAIN CERITHllDM 4J 



Cerithium floridanum Morch 



ISTO. Vcrithiiiiii fiorUluiniDi Murch. Malacologia Blatter, XXIII, 114. 

 1892. Vcrilliiinii /loriilaniiiii Dam,. Traus. Wagner Free Institute of Sci., Phila., 

 III. pt. 2. Dec. 282, pi. 14. fig. 10. 



Measurements : Length, :'>4.2 iiuii. ; greatest diuuieter, 14 mm. ; apical angle, 

 2!)°, changing to 22° on the twelfth volution ; sutural angle, 86°. 



The protoconch of the specimen studied is much worn, but is appar- 

 ently of the same form as that of Cerithium adansoni. The succeeding 

 three vohitions are too much worn to show the ornamentation. The first 

 volution on which surface features appear distinctly is the fifth, which 

 has a diameter of 1.9 mm. It bears ribs and two strong spirals. The 

 shoulder is long and has three fine spirals, with a sub-sutural band com- 

 posed of two elevated spirals. A single spiral is intercalated between the 

 two strong ones, and the lower slope of the volution is very short. The 

 earlier whorls of the shell bear an irregular number of varices averaging 

 about two or three on a volution. On the sixth and seventh volutions the 

 sub-sutural band gradually breaks up into a row of nodes and the spirals 

 become larger, but do not increase rapidly in number. On the eighth and 

 ninth volutions the larger spirals become nodose where crossed by the ribs, 

 and on the next volution the nodes of the sub-sutural row and those of 

 the first primary spiral become larger than the others and of equal 

 strength. At the same time the nodes of the second primary spiral be- 

 come weaker. On the two succeeding volutions the large nodes just 

 below the suture and those of the upper primary spiral are in line verti- 

 cally, forming distinct ribs, while the nodes of the lower primary spiral 

 are small and twice as numerous as those of the upper row. The spirals 

 on both the shoulder and lower slopes of the whorl alternate in strength 

 according to their order of introduction and are strongly defined by the 

 deep, narrow grooves between them. On the thirteenth and last volution 

 the nodes of the lower primary spiral become very small and numerous — 

 a mere line of beading around the shell. 



The body volution and the aperture are much broken, but the inner lip 

 is preserved, showing that it has a thick callus with a blunt posterior 

 tooth, and the anterior canal is short and rather widely open. 



Horizon and localities : Plioeenic. Caloosahatchie heds and Osprey. Man- 

 atee County, Florida. 



No. 12568, American Museum collection. 



Eemarks : The adult ornamentation of this little shell shows some 

 variation from the figure given by Dall [1892, plate 14, fig. 10] in the 



