INSTITUTE OF SCIENCE, PHILADELPHIA. 43I 



Tuomeyi, but the shell figured is immature and probably the young of C. 

 gibbosa Rang, still found living on the coast. Dr. Meyer's Boviconiu, the 

 larval form of a Csecid wrongly referred by him to the Pteropoda, has been 

 already (p. 296) discussed. 



There would appear to be no reason, in the case of pelagic shells like 

 Pteropods, why they might not, after having once gotten into equilibrium 

 with their environment, persist unchanged almost indefinitely, since they are 

 free from the influence of geological changes which affect the shores, and the 

 «ea must have been very much the same for an incalculable period of time. 



Family CAVOLINIID^. 



Genus VAGINELLA Daudin, 



Vaginella chipolana n. s. 



Plate 23, figures 4, 5. 



Older Miocene of the Chipola beds on the Chipola River, one mile below 



Bailey's Ferry, Calhoun Co., Florida, Burns. 



Shell small, polished, marked only with fine incremental lines ; posterior 

 end truncate, the foramen small, circular; on each side of it, extending in a 

 direct line a little more than one third the length of the shell, is a fine, 

 threadlike keel, which gradually fades away ; transverse diameter nearly twice 

 the antero-posterior diameter ; shell inflated, the ventral surface more so than 

 the dorsal, but the dorsal and ventral plates resemble one another more nearly 

 toward the anterior end ; anterior foramen as wide as the shell, marginate, the 

 dorsal margin with a median flexure, the ventral simply arched, the whole 

 margin in the completely adult shell somewhat reflected. Alt. of shell 5.5 ; 

 transverse diameter 3.2; antero-posterior maximum diameter 1.75 mm. 



This neat little shell appears to be rather common at the locality men- 

 tioned, but is rarely found in an absolutely perfect state. It is not sufficiently 

 like the Californian species to need comparison. 



Genus CUVIEBINA Boas. 

 Cuvierina columella Rang. 



Older Miocene of the Chipola beds, from the lower bed at Alum Blufif, 

 Chattahoochee River, Florida, Burns ; living in both oceans from N. lat. 43° 

 to S. lat. 40°, floating at or near the surface. 



Two specimens of this well-known and characteristic Pteropod were 

 obtained, as noted, by Mr. Burns. One of them is as perfect as if collected 

 yesterday from the surface of the sea, though, of course, less translucent. 

 They are absolutely indistinguishable from the recent shell. The specific 

 name of this species is a good Latin word, and stands in no need of alteration 

 into " columnella," as some inexperienced writers have hastily concluded. 



The genus is more commonly known as Cuvieria, a name preoccupied in 

 another department. 



