70 



SHELLS AND SHELL-FISH. 



one is slightly iiiflectedj and distinctly toothed. There 

 is still wanting another genus possessing some of the 

 characters hoth of Vexilla and Cassidarla: this genus 

 is Oniscia Sow._, where the inner lip is still more in- 

 flected and toothed, and the spire much shorter than in 

 Vejcilla, but yet with something of the protruding basal 

 chaniiel and general aspect of Cassidaria. As Mr. 

 Sowerby has judiciously alluded to this affinity, we need 

 not defend its existence. The circle of the Nassince 

 thus becomes closed ; since we have returned to Cas- 

 sidaria, or to that genus with which we began. 



(61.) We shall now see how beautifully this na- 

 tural series coincides with that of the Cassince, and 

 rightly estimate the additional value attached to the 

 genus Cyprcecassis, without which an important link 

 would be altogether wanting. 



Analogies of the Nassin^ and the Gassing. 



Genera of 



Nassa. 



Cyclonassa. 

 Vexilla. 



Oniscia. 

 Cassidaria. 



Analogical Characters. 



Typical ; inner lip much develop. ^ 



ed ; spire not depressed ; base | 



of the pillar internally cari- ^ 



j nated ; the basal canal reflected j 



l_ backwards. J 



Spire very short, more or less de 



pressed ; the basal canal trun 



cated. 



Aperture very effuse; outer lip 



often crenated. 



ner lip spreading, but 



argined ; outer lip thick, 



both lips striated and 



"Ventricose; generally tubercu- 

 lated ; basal canal curved.back- 

 wards. 



H 



Genera of 

 Cassin.??. 



Cassidea. 



Bolium. 



f Harpa. 



Cyprcecassis. 



Cassis. 



To dilate upon this table, would be almost implying 

 that our conchological readers were purblind. And yet, 

 for those who are not scientific, we may advert to the 

 intimate resemblance which some species of Nas.m bear 

 to the small helmet-shells in Cassidea ; so that, but for 

 their size, a superficial tyro would mistake one for the 



