Most of the original diagnosis must also be dropped, tlie parts above 

 quoted being all that it is desirable to retain. The present descrip- 

 lion is written from notes and drawings made on a careful examina- 

 lion of the broken type. The lines of growth show that, so far from 

 being " cornute," the species is remarkable for the absence of beak, 

 — the margins being more equally rounded even than in P. nhfvsa, 

 which in shape it somewhat resembles. The hinge is almost exactly 

 like that of C. claviculata, jun., but differs in the somewhat greater 

 proportionate length of the clavicle, and in the unwonted size and 

 sharp pointing of the anterior tooth. The new name has been chosen 

 to record this peculiarity, rather than follow the modern custom of 

 naming from the author of the mistake. The best naturalists occa- 

 sionally err ; but corrections can be made without affixing a false com- 

 pliment in perpetuity. 



6. ?Clidiophora discors. Shy. (Pandora d.), P. Z. S. 1835, 

 p 99 ; Sp. Conch, f. 29. 30. 



The type has not been discovered ; the figure and diagnosis only 

 relate to the outside ; and the habitat is not stated. The genus is 

 therefore doubtful ; but in shape it resembles the young of C. clavi- 

 culata. 



7. ? Clidiophora arcuata, Shy. {Pandora a.), Sp. Conch, f. 27, 

 28 ; P. Z. S. 1835, p. 93 ; Hani. Rec. Shells, p. 49. 



The worn valves in the Cumingian collection do not allow of a 

 confident determination of the genus. 



Genus Ccelodon*. 



Testa Pandoriformis : valva sinistra dentibus duobus, eicatrirem 

 adductoris anticam versus radiantibus, lamina infra cavernosa 

 junctis : ossiculo nullo . sinu pallii nulla. 



The shells of this group vary considerably in shape and dentition 

 in the different species ; but agree in this, that in the left valve there 

 is a kind of tent, formed by a thin laminated roof lying on the top of 

 two diverging teeth. It is hard even to guess what is the use of this 

 (perhaps unique) structure ; especially as its opening is not towards 

 tlie body of the shell, but directly facing the anterior adductor. It 

 is seen at once on opening the typical species, which was well figured 

 by Sowerby, Sp. Conch, f. 22. In the aberrant forms it might easily 

 be overlooked, and a glass is needed to detect it in small specimens; 

 but if it exists, the shell can be supported on a pin thrust into the 

 " hollow tooth." When more species are known, the group may 

 require subdivision, the C. Jlexuvsus especially presenting a marked 

 transition to Clidiophora. In that genus the posterior part excels 

 in development ; in Calodon, the anterior. All the known species 

 are from the Eastern seas, but are very seldom seen in collections. 

 An enlarged diagnosis of the type species is offered. 



* Th. KoiXos, hollow ; dSoiv, tooth. 



228 



