350 TRANSACTIONS OF THE WAGNER FREE 



This immunity, I believe, is closely connected with the much steeper sea- 

 ward slope of the Pacific litorale, which would allow a certain proportion of 

 the shore-dwellers to retreat when slow elevation dried off the beaches which 

 were their accustomed haunts. The Pacific C. imbrkatzcm, except for the link 

 furnished by the fossils, is quite distinct from its near relative, C. spinosum, but 

 in the Pliocene fossils the intermediate forms are more numerous, and there 

 the two can hardlj? be regarded as distinct species. 



Crucibulum auricula var. spinosum Sowerby. 



Calyptrcza spinosa Sby., Genera, xxiii. figs. 4, 7, 1824. 

 Crucibulum spinosum Gabb, Geol. Santo Dom., p. 241, 1873. 



Dispotaa duniosa Conrad, Am. Journ. Sci. xli. p. 346, pi. 2, fig. 9, 1841 ; young shell. 

 Crucibulum dumosum Tuomey and Holmes, Pleioc. Fos. S. Car., p. 109, pi. ,xxv. fig. 6, 1857; 

 young shell. 



Shell with radiating riblets more or less ornamented with tubular spines 

 or tubercles. Fossil in the Older Miocene of Santo Domingo, Gabb ; in the 

 Newer Miocene of North and South Carolina, Conrad and Holmes ; in the 

 Pliocene of the Caloosahatchie beds and Alligator Creek, Florida, Dall and 

 Willcox ; in the Post-Pliocene of California, Conrad ; and living from Monte- 

 rey, California, to Panama on the Pacific Coast. 



In the young of this species the cup, especially if a little broken, resem- 

 bles that of Dispotcea, but in the adult its margin is wholly disengaged from 

 the wall of the shell. The Caloosahatchie specimens agree in the minutest 

 particular with recent specimens from California, though both exhibit a wide 

 range of variation. 



Section Dispotcea (Say) Conrad. 

 Orucibulura constrictum Conrad. 



Dispotcea constricta Conr., Bull. Nat. Inst. ii. p. 194, pi. i, fig. 2, 1842 ; Medial Tert., p. 80, 



pi. 45, fig. 4, 1845. 

 Crucibulum costata Tuomey and Holmes, Pleioc. Fos. S. Car., p. 107, pi. 25, fig. 4, 1857 ; 



not C. costata Say. 



Older Miocene of Jericho, N. J., and the Orthaulax bed at Ballast Point, 

 Tampa Bay, Florida, Burns and Dall ; Chesapeake Miocene of the Choptank 

 River and St. Mary's Co., Md., of the James River, Va., of North Carolina, 

 of Peedee River, S. C, and of the upper bed at Alum Bluff, Chattahoochee 

 River, Florida. 



The character for which Conrad named this species was due to an indi- 

 vidual distortion, but the species is a good one. It is liable to be mistaken 

 for C. auricula var. costata Say, from which it differs by the adherent cup in 

 the adult state. 



Tuomey and Holmes have figured a fine normal specimen under the name 

 of costata. I have not seen this species from the Pliocene. 



