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Dr. J. Allan Thomson—On the Terebratellide. 501 
of Zaqueus or any other known genus, and justify the erection of 
a new genus. 
ALDINGIA, gen. nov.! 
Genotype Zerebratella furculifera, Tate. 
Until the growth stages of Aldingia are known, the subfamily of 
the Terebratellidz to which it belongs cannot be determined, but it 
appears not unlikely that it passes through a Miihlfeldtiform stage 
in its ontogeny, and that the descending lamelle uniting on the septum 
are comparable to the sides of the primitive ring in Mihlfeldtia. 
Genetic Stocks In THE MaGeLianin® and DaALuLininzZ. 
In a former paper (1916, No. 2) I have endeavoured to show that 
Magellaniform loops have been produced by parallel evolution in at 
least three distinct stocks, each characterized by its own type of 
cardinalia? and beak characters. There are, doubtless, many other 
stocks equally worthy of generic recognition in the Magellanine, but 
the evidence for their separate attainment of the Magellaniform loop 
is not yet forthcoming. 
Dallina floridana, Pourtales. Anterior-ventral view of cardinalia of dorsal 
valve. SR. socket ridge ; H. hinge-plates ; C. crural bases; S. septum. 
There is no cardinal process. Enlarged about 23 nat. size. 
Thanks to Jackson’s valuable observations we are now able to 
recognize similar evolutionary stocks in recent Dallinine. Thus 
Terebratalia and Thomsonia are shown both to possess hinge-plates 
and a similar type of cardinalia differing markedly from that in 
Dallina and Macandrevia. As the type of the folding and the beak 
characters are also similar in Thomsoniaand Terebratalia, these genera 
doubtless form one evolutionary stock. 
Jackson states that Dallina possesses typically Magellaniform 
eardinalia, but it appears useful to draw a distinction. The only 
‘1 Named from Aldinga, South Australia, a notable locality for Tertiary 
Brachiopods. 
2 This term I intended as a (Latin) neuter plural, but in my former paper it 
was used as a sincular noun, and I had not an opportunity to revise the proofs. 
