56 PROCEEDINGS OF THE ACADEMY OF [March, 



In counting the whorls, it has been attempted to have the end of 

 the first whorl come in about the position shown in the figure. It is 

 impossible to make an absolutely exact count, but if care is used there 

 will seldom be much of an error in the last whorl. As stated above, 

 the method is purely arbitrary, but it seemed to the writer to be the 

 only practical way in which the statistics of the development of orna- 

 mental features could be arranged. 



Fig. 2. — Volutilithes limopsis Conrad. Matthew's Landing, Ala. Apex 

 enlarged, showing smooth stage followed by the curved rib stage, which begins 

 in the latter part of whorl four. Whorl five shows the cancellated stage. 

 Length = 1.6 mm. 



Volutilithes limopsis Conrad. 



Locality — Matthew's Landing, Ala. 



This species was originally described by Conrad in Jour. Acad. Nat. 

 Sci. Phila., 2d Series, Vol. IV, p. 292, PI. 47, fig. 24. 



Whorls 1, 2, 3 — Smooth and rounded. 



Whorl 4 — Smooth and rounded, except toward the end, where the 

 curved rib stage may start. 



Whorl 5 — The curved rib stage often commences early in five, per- 

 sisting as a rule for about a quarter of a whorl. The cancellated stage 

 follows abruptly with its straight, tubercled ribs. These tubercles 

 are largest at the suture, decreasing regularly in size anteriorl}^ on each 

 rib. Each tubercle is connected with the corresponding tubercle of 

 the next rib by a faint spiral. A shoulder angle is never developed. 



Whorls 6, 7 — Characterized by the cancellated stage and much like 

 the latter part of five. 



Whorl 8 — Characterized by the cancellated stage and much like 

 six and seven. The tubercles nearest the suture are the strongest, and 

 they diminish in size regularly as the rib is followed anteriorly. The 

 ribs are also less prominent anteriorly, disappearing entirely on the 

 branchial siphon. Spirals cover the entire whorl. 



Whorls 9, 10 — jNIuch as in eight, the cancellated stage still persisting. 



