364 CANCELLARIAD^. 



occurs throughout the Clyde region and the Hebrides, and 

 around the Zetlands ; also on the east coast of Scotland, 

 and as far south as the coast of Northumberland. Mr. 

 Barlee has taken it on the west coast of Ireland. It 

 ranges throughout the Boreal and Arctic Seas, and dates 

 in ours from the epoch of the coralline crag. 



CERITHIOPSIS. Forbes and Hanley. 



Shell in all respects according with the characters of 

 Ckkithujm. Operculum corneous of concentric elements, 

 nucleus terminal. Animal widely different : its head rather 

 broad and short, flanked by two obtusely subulate tentacles, 

 Avidening slightly at their bases, and set well apart ; eyes 

 placed centrally at their origin. Mouth inferior, furnished 

 w'ith a retractile proboscis ; tongue armed with teeth 

 which appear to resemble in their arrangement those of 

 Trichotropis. Mantle not reflected, furnished with a 

 rudimentary siphonal fold. Foot oblong, subquadrate in 

 front, where it is furnished superiorly with a mentum, 

 obtuse behind, grooved for half its length below, the 

 groove terminating in a perforation : operculigerous lobe 

 w^ell developed. 



In instituting a distinct genus for the Cerithium tuber- 

 culare, however repugnant the proceeding may be to 

 conchological notions, seeing that the shell alone will not 

 enable us to speak even as to its tribe, we feel sure all 

 malacologists, when once they have looked to the structure 

 of this remarkable animal, must agree in the course we 

 have taken. Exotic forms of Cerithiopsis will probably ere 

 long be detected among the crowd of Cerithia. 



This genus has distinct affinities with the Pyramidellidee ; 

 but the general assemblage of its characters induce us pro- 



