404 PTEAMIDELLID^E. 



possessing the Muricidal retractile proboscis, as well as the 

 rostrum of the Littorinidan race from whence it has proceeded. 

 In the Mollusca, there is nothing extraordinary in this com- 

 posite structure ; we see it exemplified in the different plans 

 of reproduction. All these circumstances point out the com- 

 plexity and difficulty of the investigation of these singular 

 animals ; an hour or a day's examination is of little avail ; 

 they must be constantly studied for weeks, with a regular 

 supply of fresh specimens, as torpidity always ensues in less 

 than twenty-four hours ; and they must not only be examined 

 by day and sunlight, but also by the argand-lamp and wax- 

 taper. We must literally attend, for these diminutive crea- 

 tures, to the precept 



" Nocturna versate manu, versate diurna." 



The observations on each species w r hich have appeared in 

 the ' Annals of Natural History ' during the last three or four 

 years will not be strictly amalgamated, but merely placed 

 together to show the progress of science in new discoveries 

 and rectifications, including the year 1854 : every reader will 

 easily cull from them the information he requires. 



Before I enter on the descriptive notes, I present a few 

 additional observations, and supply some omissions, on the 

 peculiarities of the Chemnitzia, in which I shall endeavour to 

 dispel some of the clouds that still envelope this difficult and 

 interesting group; and I shall also give a short catalogue 

 raisonne, that is, a remark or two on every British Chemnitzia, 

 whether genuine or apocryphal, sweeping away the phantoms 

 of the genus, and thus establishing the means of identifying 

 every genuine species ; whereby the collector will be enabled 

 to complete his list without fretting himself by endeavouring 

 to obtain many recorded objects, which may as well be looked 

 for as the philosopher's stone or perpetual motion. This 

 review of the tribe, which I call Chemnitzice, and others of 

 the moderns partly Chemnitzia and partly Odostomiee, will, 

 I think, interest and be singularly useful both to the malaco- 

 logist and conchologist. In my expose I shall show that this 

 group, from its comparative difficulty and obscurity, has long 



