108 MITRID^. 



Mr. Andrew Garrett* suggests that the Polynesian shells 

 which have been described by H. and A. Adams under the name 

 of Thala, as a subgenus of 3Iifra, are more nearly related to 

 Pleurotomida% the so-called folds of the columella not being- 

 true plaits, but simply more or less ii-regular transverse 

 rugosities precisely of the same character as those upon certain 

 species of ClathureUa and Cithara of that family. Two species 

 of true Mitra? have, however, been referred to Thala ^ and 

 I have preferred to retain the genus in the Mitridse for the 

 present, upon duly weighing the value of its known character- 

 istics. Mr. Pease's genus Mitropsiis is excluded, being a 

 member of the family Columbellidre, Finall}-, Mitroniorpha, 

 A. Ad., appears to be more nearly related to the Pleurotomidaj, 

 several of its species having been described as Daphnellse. 



Synopsis of Gene^^a. 



MITRA, Lamarck. Shell fusiform, thick; spire elevated; aperture 

 small, narrow, notched in front; columella transversely, somewhat 

 obliquely plicate; outer lip thick, smooth within, not variced 

 externally. Dentition, PI. 2, figs. 9, 10, 11. 



[VoLUTOMiTRA, Gray. Separated from Mitra on account of the peculiar 

 dentition of an Arctic species, V. Grcenlandica. Twenty additional 

 species have been included in the genus by H. and A. Adams ; they 

 are all !Mitras in appearance, and the dentition of none has been 

 examined except that of V. cornea^ which decidedly differs from 

 Orcenlandica , and is of the regular i/iYra-type. Dentition of V. 

 Qrcenlandica. PI. 2, fig. 8.] 



THALA, H. and A. Adams. Small, narrowly fusiform, sculptured or 

 smooth, last whorl attenuated and recurved below; outer lip thickened, 

 straight or incurved in the middle, liratc internally, with a slight 

 sinus at the hind part. Dentition unknown, 



[Strigateli.a, Swainson. Shell ovate or Columbelliform, solid; spire 

 acuminate; whorls smooth or transversely striated, usually covered 

 with an epidermis; inner lip with a callosity at the hind part; outer lip 

 usually thickened in the middle, and inteinally grooved or dentate. 

 Dentition unknown.] 



* Catalogue of the Polynesian Mitridae, in the (English) Journal of 

 Conchology, iii. A very valuable paper, from which I have drawn 

 largely for these pages. 



