GASTKROPODA PECTINIBK ANCHIATA. 255 



HARPA, Lamarck. 



The Harpa: are easily recognised by the projecting transverse ribs on the 

 whorls ; the last of which forms a lip on the margin. The shell is beautiful, 

 and the animal has a very large foot, pointed behind, and widened in its 

 anterior portion, which is distinguished by two deep emarginations. The 

 eyes are on the sides of the tentacula, and near their base. It has neither veil 

 nor operculum. The 



PURPURA, Brugueir. 



Is known by its flattened columella, which is trenchant near the end 

 opposite to the spire, and which, with the external margin, forms a canal 

 there, sunk in the shell, and not salient The animal resembles that of a 

 true Buccinum. 



The remaining subgenera are Concholepas, Cassis, Cassidaria, and Terebra. 



CERITHIUM, Brugueir. 



A shell with a turriculated spire ; the aperture is oval, and the canal short, 

 but well marked, and reflected to the left or backwards. The animal has 

 a veil on its head, and is furnished with two separated tentacula, on the side 

 of which are the eyes, and with a round horny operculum. Many are found 

 fossil. 



MUREX, Linnceus. 



This genus comprises ah 1 those shells in which there is a salient and straight 

 canal. The animal of each subgenus is furnished with a proboscis, long 

 approximated tentacula, on the external side of which are the eyes, ami with 

 a horny operculum ; the veil on the head is wanting; and, the length of the 

 siphon excepted, it otherwise resembles that of the Buccina, Brugueir divides 

 them into genera, which have been since subdivided by Lamarck and de 

 Montfort. The 



M uitra, Brugueir t 



Includes all those which have a salient and straight canal, with varices 

 across the whorls. 



RANELLA, Lamarck. 



Characterised by opposing varices, so that the shell is bordered with them 

 on both sides. Their canal is short, and their surface studded with mere 

 tubercles ; margins of the aperture plicated. The 



Fusus, Brugueir. 



Comprises all shells with a salient and straight canal, which are destitute of 

 varices. 



TURBINELLA, Lamarck. 



Also consists of shells with a straight canal, and without varices, distin- 

 guishable by the large transverse plicae on their columella, which extend the 



