PRESIDENT S ADDRESS. 69 



considers, for reasons which in themselves are not very convincing, 

 that Conularia is a mollusc appearing to resemble the primitive 

 Cephalopoda more than any other forms, but she prefers " to regard 

 Conularia as a member of an extinct group equivalent to the 

 Cephalopods, and deiived with them from the same simple shelled 

 ancestor." As such, then, we leave them in our tables. 



The Pelecypoda were yet earlier in their advent than the 

 Cephalopoda. Two forms have been recorded from the Cambrian. 

 The one, however, Fordilla of Barrande, is suspect and may be the 

 remains of a Pod-Shrimp. The other, Modioloides priscus, Walcott, 

 founded on an oval, internal cast 2 mm. long, exhibiting an anterior 

 adductor scar and apparently a simple pallial line, is considered to be 

 an early Protobranch. 



Prom British Upper Cambrian (Tremadoc beds) come some obscure 

 casts, which have been referred to several primitive genera — one 

 doubtfully to Orthonota, which is also a Protobranch, others to 

 Palcearca and Glyptarca, genera now sunk in Cyrtodonta. The exact 

 position of this latter genus is uncertain ; though usually placed with 

 the Arcacea, its members, with their mixture of hinge-characters, may 

 rather be regarded as linking the Protobranchs with the Pilibranclis. 

 Associated with these are some mytiloid shells and two pterin oid 

 examples from an unknown horizon {26, p. 200 ; Brit. Mus. 

 Registered No. 48762 and No. I. 2612), that may belong to 

 Ambo7iychia or Bysso7iychia, in Avhich case they would form some of 

 the earliest representatives of the Pectinacea, as defined by Pelseneer, 

 and usher in the Filibranchs, of which suborder more unmistakable 

 examples are met with in the succeeding Ordovician period. Obviously 

 these ancient bivalves require to be carefully re-studied in the light of 

 the researches of the late Felix Bernard {2), whose premature demise 

 was a most serious loss to Malacology. 



Of the next order, the Eulamellibranchia, no representatives appear 

 earlier than the Silurian, where a form doubtfully referred to Lucina 

 (Submytilacea) has been detected, as well as one of the more highly 

 specialized Anatinacea, Rhytimya. The Ostracea, represented by 

 Palceopimia, only came in with the Devonian, in which, too, the first 

 fresh-water shell, Archanodon, is found, its record for the Lower 

 Devonian falling to the credit of our member, Mr. E.. Bullen Newton 

 {32). An early example of the Myacea, Palceosolen, likewise is found 

 in beds of this age. 



Of the most specialized order of the Pelecypoda, the Septibranchia, 

 no example is met with at least till Jurassic times, if CorbiireUa be 

 admitted to this group, or with certainty till the Cretaceous, where 

 Liopidha makes it appearance, followed by Poromya in the 'I'ertiary. 



On the whole, therefore, due allowance being made for the 

 poverty of the early materials, the Pelecypoda fairly conform in 

 their geological history to the conclusions based on the study of 

 their morphology. 



The Scaphopoda, having been derived, according to Pelseneer, from 

 the same stock as the Pelecypoda and Gastropoda, might have been 

 expected to share an equally early advent. It is true tliat one fossil 



