1898.] NATURAL SCIENCES OF PHILADELPHIA. 283 



rapidly widening whorls. The only species, B. taylori Pfr., inhabits 

 the table land of Lower California. 



Genus CCELOCENTRUM Crosse & Fischer. 



The hollow and usually vertically ribbed axis is unlike any of the 

 Antillean types, although radiating spines, such as Dall describes in 

 C. astrophorea, recall certain forms of Gongylostoma. In the section 

 Spartocentrum Dall 11 there is a spiral inflation and no vertical rib- 

 lets. 



Genus CERION (Bolt.) Morch. 

 See Proc. Acad. Nat. Sci. Phila., 1896, p. 315. 



This genus has generally been placed in tfye neighborhood of 

 Pupa, but it is not closely allied to that group in shell characters 

 and is entirely diverse in genitalia. It may possibly belong to the 

 Odontostominoz ( Odontostomus, Tomigerus, Anastoma) of South Amer- 

 ica ; but we prefer to associate Cerion with the Holospira and Euca- 

 lodium groups of Urocoptidce. 12 



As this genus has been made the subject of special papers by Dr. 

 W. H. Dall and by the present writers, it need only be said here 

 that it differs from the other genera in being strictly littoral in dis- 

 tribution, never straying far from the sea shore. The Miocene forms 

 (Eostrophia) are probably aberrant rather than primitive, in lack- 

 ing parietal and axial laminae. 



Genus MEGASPIRA Lea. 



A Brazilian group very peculiar in its polygyrate shell with large, 

 rounded nuclear whorls, plicate columella and peculiar internal arma- 

 ture, somewhat recalling Gongylostoma, Idiostemma, etc. This has 

 been described and figured by Gabb. 13 The dentition we have now 

 examined (PI. XVII, fig. 1), the radula having been found in a dry 

 shell. There are 28'1"28 teeth, arranged in slightly sinuous trans- 

 verse rows, and of the type usual in ground snails, much like those 

 of Eucalodium, Berendtia, etc. 



11 See Xautilus IX, p. 51 (Sept., 1895), type Ccelocentrum irregulare Gabb. 

 The genus Teneritia Mabille, Bull. Soc. Philomathique de Paris, (Ser. 8), Vol. 

 IX, p. 79(1897 or 1898) is a synonym of Spartocentrum. Types Berendtia digued 

 and B. minorina Mabille. M. Mabille is perfectly right in separating his 

 group from Berendtia, but he overlooks the only really important differential 

 character, viz., the hollow axis. 



12 Dall has hinted at the same relationship. See Proc. U. S. Nat. Mus., 

 XIX, p. 347, 348, 1897. 



13 American Journal of Conchology II, p. 64. 



