The Austral Rhynchonellacea. 171 



tiguous areas of the southern hemisphere do not seem to have been 

 .satisfactorily defined, the opportunity is now taken, with the help of a 

 great deal of new material, to review the evidence already published. 

 This, we hope to show, will prove that the southern stock of these 

 multiplicate Cainozoic and Recent forms is generically distinct from 

 Hemithyris, and seems to have been derived from a common Mesozoic 

 type long before the period of the disintegration of the early Ant- 

 arctic continent. 



Until 1910, the Australian rhynchonellids, both fossil and recent, 

 were referred to the genus Rhynchonella in the unrestricted sense. In 

 that year, Mr. S. S. Buckman published a paper on Antarctic Fossil 

 Brachiopoda2, in which he described several fossil forms of rhynchonel- 

 lids, two of which had been previously recorded under the genus 

 Rhynchonella {R. squamosa, Hutton, and R. plicigera, Ihering). These 

 fossil forms Buckman referred to d'Orbigny's genus Hemithyris, which 

 in the original description Is stated to possess no dental plates. 



In 1914, one of us3 referred to Button's species, squamosa, as be- 

 longing to- the genus Acanthothyris of d'Orbigny, on account of the 

 tendency of this form to develop a spinose character along the 

 costae. This spinose character is fundamental in d'Orbigny's Jurassic 

 genus. The genotype of Acanthothyris is A. spinosa, Schlotheinj sp. 

 of the Inferior Oolite of England*; but, as we hope to show later, the 

 northern Jurassic and the southern Cainozoic forms belong to different 

 stocks, and therefore the spinose character is an example of conver- 

 gence of form. 



In his revision of the Fossil Brachiopoda, Prof. Chas. Schuchert* 

 had included the living spinose form, Rh/ynchonella doederleini of 

 Davidsons, as a representative of the genus still living in Japanese 

 Seas. From the present evidence this species seems related to the 

 southern types, which fall into the new genus Tegulorhynchia. 



In reviewing all the evidence given by previous authors, and in the 

 light of a large amount of material recently collected from Victorian 

 and other Australian deposits, we find the results necessitate the 

 establishment of a new genus which will include forms of the Rhyn- 

 chonella squamosa type, the distinctive characters of which are dis- 

 cussed in a later section. 



II. — Cainozoic and recent Austral Rhynchonellids: 

 With Critical Notes. 



antipoda, Hemithyris, Thomson. 

 Thomson, 19182, p. 117. 



"In H. antipoda, the ribs are similar In size to 

 H. nigricans, but rather more numerous, and are inclpi- 

 ently spinose." 



2. Buckman, 1910, pp. 10-14. 



3. Chapman, 1914, pp. 166, 167, fig. 89F. 



4. cf. Davidson, 1852, p. 71, pi. xv., figs. 15-20. 



5. Schuchert, in Zittel, 1913, p. 400. 



6. Davidson, 1887, p. 172. 



