240 PYRAMIDELLID^. 



(but, according to Loven, furnished with a minute conical 

 process on each side). 



In retaining the name Chemnitzia for a group of very 

 beautiful and easily recognized little shells, it is necessary 

 that we should defend both the adoption of the assemblage 

 as a genus at all, and, when we have done so, why we 

 give it the name proposed by M. Alcide d'Orbigny, in 

 preference to other appellations. Moreover, in using this 

 generic term, we are doing so in a somewhat peculiar 

 sense, bringing together in it not only Chemnifzitx, strictly 

 so called, but also certain species which have been con- 

 stantly regarded as Odostomia, in the restricted meaning 

 of the last named genus. On the other hand, we refer to 

 Odostomia, a few forms which are more usually regarded 

 as Chemnitzieje. 



Although the history and literature of true mollusks have 

 been fully and ably discussed by our friend, Mr. Gwyn 

 Jeffreys, in his excellent Memoir " On the recent species 

 of Odosfomia,'''' communicated to the British Association 

 at Swansea, and afterwards published in the " Annals of 

 Natural History," it is nevertheless necessary to say a word 

 or two respecting the principal appellations ajiplied to 

 them. Three authors have regarded the ribbed shells here 

 described under Chemnitzia as forming a natural genus. 

 Risso termed them Turhonilla^ adopting a manuscript 

 name given to them by Leach ; Lowe defined and deter- 

 mined admirably both animal and shell under the name 

 Parthenia, and Alcide d'Orbigny constituted and defined 

 for them a group under the name of Chemnitzia. The 

 last name which stands second in point of date, but which 

 might be objected to, since, in the work in which it ap- 

 pears (the " Natural History of the Canaries," by Webb 

 and Bartholet), it is given to a subgenus of 3Ielania, has 



