224 SYSTEMATIC PALEOXTOLOGY 



Description.^^' Conical in shape, as is usual in the genus. Size small. 

 Costae tall and thin with crenate margins. Beginning with &, 6 more 

 costae are soon developed, making 12, between which in the intercostal 

 furrows are double rows of perforations. The 12-costal condition exists 

 for about 1.5 mm. from the base, when 12 more costae are introduced. 

 The costae on the basal portion of the corallum are very slightly larger 

 than they are on the upper portion; they are not so prominent on the 

 basal portion as in Turbinolia pliaretra. In the extreme upper portion 

 24 rudimentary costae are introduced, making the total number 48, 

 twice as many costae as septa. In the intercostal furrows, after the de- 

 velopment of the rudimentary costae, there are only single rows of per- 

 forations; during the 24-costal stage there are double rows of alternating 

 perforations in the intercostal furrows. The septa are 24 in number, in 

 three cycles. Those of third cycle fuse, about half-way between the 

 corallum wall and the columella, by their margins to the sides of those 

 of the first cycle. The septal faces are beset with distinct, sharp, small 

 spines. All of the septa except those of the first cycle are thin and weak. 

 Columella weak, terminated by a small hexagonal star. Height, 6.5 

 mm.; diameter of calice, 3 mm." A^aughan, 1900. 



Since the original diagnoses of this species and T. wautubbeensis ^ 

 were prepared additional specimens have come to notice, making a 

 revision of the critical remarks on these species necessary. The speci- 

 men of T. acuticostata from Popes Creek possesses a weak columella, 

 with a stellate upper termination. Additional specimens of T. wautiib- 

 heensis collected by Mr. Frank Burns at Wautubbee, Mississippi, show 

 that that species possesses costae with crenate margins. The costae 

 of the original type of T. ivautuhbeensis are probably worn. These facts 

 have shown that these two sj)ecies are so closely related that it seemed 

 that it might be necessary to unite them, however, there are still 

 important differential characters. The costal erenations of T. acuti- 

 costata are coarser than those of T. wautiibheensis, and the incisions 

 between the erenations in the former species are deeper than in the 

 latter. The columella in well-preserved specimens of T. wautubbeensis 

 is stouter than in T. acuticostata, but there is not sufficient good ma- 



iMon. U. S. Geol. Survey, No. 39, p. 88, pi. vi, lig's. 11-13. 



