342 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



The spire is somewhat worn above, so that the number of whorls 

 is uncertain. 



The genus Plochelcea Gabb belongs, no doubt, to the Mitridae. 

 It stands close to, if not to be united with, the genus Mutyca H. & A. 

 Adams, 1853, type M. ancillides Swains., with which Mitroidea Pease 

 1865, (typeM. multi'plicata Pse.), and Mownfm H.Adams, 1869, type 

 M. harclayi H. Ad., are to be united as synonyms or sections. 

 Dihaphus Philippi (1847), is another allied genus. With a knowl- 

 edge of the above mentioned genera it seems strange that Gabb re- 

 ferred Plochelcea to the Olividae. 



The type of Plochelcea is P. crassilabrum Gabb. 



Plochelaea gabbi Pils. and Johns. Plate. XXIV, flg. 7. 



Proc. A. N. S. Phila., 1917, p. 166. 



XANCIDAE. 



Turbinellidae of authors. 



The replacement of the name Turbinella by Xancus is one of the 

 outrages against scientific nomenclature consequent upon the 

 adoption of Bolten's Museum as a source of generic and specific 

 names. The disappearance of the name Turbinella necessitates 

 alteration of the family name. 



This family is remarkably well developed in the Santo Domingo 

 beds. 



Xancus rex Pils. and Johns. Plate XXVI, figs. 5, 8. 



Proc. A. N. S. Phila., 1917, p. 167. 



The spire is longer than usual in X. scolymus, not shorter as stated 

 in the original description. The inner lip often has the callus de- 

 tached at the edge. The size of adults varies a good deal. 



It is an abundant species, mistaken for A', validus by Gabb, 

 Maury and others. 



Xancus validus (Sowerby) Plate XXV, flg. 3. 



Turbinellus validus Sowb., Q. J. Geol. Soc. vi, 1849, p. 50. Not of Gabb or 

 Maury. 



This species has been misunderstood by Gabb and Maury, owing 

 to Sowerby 's qualified comparison with Turbinella scolymus. 

 The original description, however, is good, and the comparison not 

 strained when one remembers that in 1849 Turbinella comprised 

 also Vasum, Latirus and other genera. 



The shell is obesely fusiform, ponderous. The embryonic stage 

 is unknown, but the early and middle neanic whorls have thick, 



