INSTITUTE OF SCIENCE, PHILADELPHIA. 395 



Calliostoma "Willcoxianum n. s. 



Plate i8, figure i. 



Miocene of Duplin Co., N. Cai"., Burns; Pliocene of the Caloosahatchie 

 beds, Dall and Willcox ; and of Shell Creek, Fla., Willcox. 



Shell with nine whorls, the nucleus small, smooth, inflated, of nearly two 

 whorls, the remainder of the shell closely spirally sculptured ; the form is 

 that of C. philantliropus, of which this species is without doubt the Pliocene 

 representative, and the shell is therefore best described differentially ; the 

 sculpture of Willcoxiamini is of stronger, more close-set threads, with more 

 pronounced beading, narrower interspaces and less angular periphery. The 

 spirals on the base are stronger, stouter and more rounded, those near 

 the umbilical region are obscurely beaded, with sharply cut interspaces. The 

 excavation of the columellar callus is more pronounced than va. philanthropus, 

 and there is sometimes a rounded pit, though no perforation. The very 

 young are very depressed, have a minute but deep umbilicus, with two 

 strongly beaded projecting spirals next to it, from which the base slopes away 

 to the periphery, with sharp, plain spiral sculpture. In pliilantliropus of the 

 same size the base is flatter, imperforate, and with a smooth, flat area between 

 the sculpture around the umbilicus, and a single sharp thread near the periph- 

 ery. The difference between the two forms is much more marked in these 

 young shells than in the older ones. The adult measures 15 mm. high and 

 16 mm. in greatest width. 



The changes which we observe between the Miocene and Pliocene species 

 of this type — i. ^., stouter and closer sculpture and more rounded periphery — 

 continue in the same line into the recent fauna, where the recent representa- 

 tive, C. eiiglyptum A. Adams, doubtless the descendant of C. pliilantliropus 

 and Willcoxiamini, is more rounded than the latter, and with closer and still 

 more beaded, though less prominent, sculpture, while its variability is much 

 less than in the Miocene shells. The Miocene specimen of C. Willcoxianum 

 obtained by Mr. Burns is a very young shell, but appears to agree with the 

 Pliocene specimens. 



Calliostoma bellum Conrad. 

 T7-ochus bellus Conrad, Journ. Acad. Nat. Sci. vii. p. 137, 1834. 

 Zizyphinus bellus Conrad, Proc. Acad. Nat. Sci. 1862, p. 569. 



Chesapeake Miocene of James River, Va., of Duplin Co., N. Car., and of 

 Darlington, South Carolina, Burns and Harris. 



This shell resembles a small C. eiiglyptum, with sparser spirals and pecu- 

 liarly prominent and universal prickly beading, especially strong on the base. 

 It is, perhaps, the precursor of the next species. 



Calliostoma roseolum var. permagnum Dall. 



Calliostoma roseolum Dall, Rep. Blake Gastr., p. 366, pi. xxiv. figs. 6, 6 a ; Bull. Mus. 

 Comp. Zool. ix. p. 45, iSSr. 



Typical form in warm water from North Carolina to Yucatan in 15 



