160 ARCID^E. 



has a differently constructed hinge-apparatus, and only 

 one, nearly central, adductor muscle. 



The first to point out the difference between Lwiopsis 

 and Pectunculus (although he retained both in the old 

 Linnean genus Area) was the celebrated Italian palaeon- 

 tologist Brocchi, who, in his i Conchiologia fossile Suba- 

 pennina/ described the species which I now propose to 

 record as indigenous to the British seas. His descrip- 

 tion and remarks are (as usual) most excellent, and he 

 especially noticed the similarity of his Area aurita to 

 the Ostrea lima of Linne in respect of the triangular 

 cavity in the hinge. The history of the present genus 

 is involved in some obscurity, owing to the rarity of the 

 work in which it was originally published. This was 

 done by Sassi in the 'Giornale Ligustico di Scienze, 

 Lettere, ed Arti ' (fascicolo quinto) for September 

 1827. The British Museum library does not contain 

 the work ; and it is only through the kindness of 

 Prof. Lessona of Genoa that I have been enabled to 

 refer to it. Nyst, in his ' Catalogue of the Tertiary Fos- 

 sils of Belgium ' (1843), professed to be ignorant of 

 Sassi's publication or its date, although Bronn, in his 

 f Lethsea Geognostica/ had given both these particulars 

 twelve years before this statement was made by Nyst. 

 The last-mentioned author, in conjunction with Gale- 

 otti, had in 1835 renamed this genus Trigonoccelius. 

 Nyst altered the name to Trigonoctelia. The late Pro- 

 fessor D'Orbigny, equally disregarding the rule of pri- 

 ority in scientific nomenclature, gave, in the ' Paleonto- 

 logie Francaise' (1844), another name, that of Pectun- 

 culina. This has been lately adopted by Dr. Chenu in 

 his very useful f Manuel de Conchyliologie et de Pale- 

 ontologie conchyliologique '; but he most unaccount- 

 ably makes Limopsis and Trigonoccelia subgenera of Pec- 



