1906.] NATURAL SCIENCES OF PHILADELPHIA. 69 



Remarks. — This race shows a regular and even ontogeny. The 

 different stages are quite distinct. The senile characters are not 

 thrown back into the spiny stage but follow regularlj^ after it, and 

 constitute the culminating feature of individual development. These 

 marks of old age are never extreme. Acceleration early in life has 

 placed the curved rib stage at the beginning of the third whorl, and 

 the cancellated stage has been correspondingly lengthened. The 

 cancellated stage is longer here than in any of the other forms con- 

 sidered in this paper except V. limopsis. This assemblage is the last 

 representative of Volutilithes in the Alabama and Mississippi Eocene. 

 It fulfills every requirement for position on the V. petrosus inain stem, 

 it is the culminant race of the stock, and has attained its characters 

 by a slow and even phylogenetic development. 

 Volutilithes haleanus Whitfield. 



Locality — Lisbon, Ala. 



Whorls 1, 2 — Smooth and rounded. 



Whorl 3 — Smooth and rounded at fii'st, but later the curved rib stage 

 begins. This persists for about a quarter of a whorl, and is then fol- 

 lowed by the straight, tubercled ribs of the cancellated stage. The 

 shoulder tubercle is just a trifle larger than the suture tubercle. The 

 shoulder angle is well marked by the end of the whorl. 



Wliorl 4 — Characterized by the cancellated stage. Shoulder angle. 

 Shoulder tubercle stronger than the suture tubercle. 



Whorls 5, 6 — Characterized by the cancellated stage and much like 

 whorl four. During these whorls the suture tubercle tends to attain 

 the same strength as the shoulder tubercle. Spirals not very well 

 marked. 



Whorl 7 — From here on the primitive cancellated stage is replaced 

 by what may be called a modified cancellated stage. The suture 

 and shoulder tubercles are now of about the same size. The ribs are 

 crowded so closely together that they are almost in contact, being 

 separated by a mere depressed line. The shoulder tubercles are so 

 close together that the general effect is that of a whorl with a shoulder 

 keel. 



Whorls 8, 9 — ]\Iuch as in seven, but toward the end the shell becomes 

 thick and the growth lines slightly irregular. The protruded mantle 

 produces only an insignificant smoothing of the preceding whorl. 



Remarks. — By a study of its early whorls it is evident that this form 

 was at some time derived from the V. petrosus main stock. Its can- 

 cellated stage closely resembles that of the races of V. petrosus until we 

 reach the seventh whorl. After that it is quite different in its general 



