The Austral Rhynchonellacea. 187 



referred to the Oolitic genus, Acanthothyris, by Schuchert.^s it seems, 

 however, that two distinct races, with senescent spinosity, were thus 

 confused. Buckman^^ has remarked that T. doederleini is " more 

 probably a spinous development of Hemithyris nigricans " ; but here 

 we may point out that, in the light of the structure of the Miocene 

 forms, such as T. coelospina and T. tuhulifera, and even of T. im- 

 hricata, that it is a direct descendant of the coelospina type rather 

 than of the nigricans type. 



T. doederleini has the beak and deltidial characters precisely iden- 

 tical with the old Miocene and even Oligocene forms, as T. squamosa 

 and T, coelata, but the extent of development of tubuli formed out of 

 the tegulated frilling has here resulted in long serial and regular 

 spines. In the conjunct deltidial plates It agrees with T. squamosa. 



Occurrence. — Dredged in 160 fathoms, in Sagami Bay, Japan. 



10. — Tegulorhynchia nigricans, Sowerby, sp. 



(PI. I., figs. 9, 10, 11, 12; pi. III., figs. 29, 30.) 



Rhynchonella nigricans, Sowerby, 1846, p. 91, 



Rhynchonella nigricans, Suess, 1864, p. 60, pi. XIV., fig. 6, 



Rhynchonella nigricans^ Kirk, 1880, p. 303. 



Rhynchonella nigricans, Davidson, 1887, p. 169, pi. XXIV., figs. 



16-19, 

 Rhynchonella nigricans, Hutton, 1905, p. 480. 

 Hemithyris nigricans, Sow., sp., Thomson, 1915, p. 388, and p. 



390, text-fig. 2a. 



Description. — The following abbreviated description is given by 

 Hutton.^^ " Shell thin, wider than long, but very irregular in shape; 

 margin crenulated, commissure sinuated. Longitudinal ribs, 20 fo 25 

 in each valve." 



"Dimensions. — Length, 19 mm.; width, 21 mm.; thickness, 10 mm." 



Observations. — This species makes its appearance in the Upper 

 Tertiary of New Zealand (probably Upper Miocene and Pliocene), where 

 it is represented by more massive shells than those of the recent 

 specimens dredged around New Zealand. In the living examples the 

 beak is usually more prominent, especially in the younger stages, 

 and the deltidial plates are discrete. In the fossil forms the plates 

 are more closely approximate. 



Thomson considers the probability that this species " is a cata- 

 genetic development of a coarsely ribbed, imbricated, Oamaruian (prob- 

 ably Miocene), species are not yet named, which differs from H. squam- 

 osa in its much coarser ribs." This view of Thomson's is upheld by the 

 evidence of the series now before us, T. thomsoni helping to connect 

 the extremities of that series. 



Occurrence. — Miocene to Recent. New Zealand. 



15. Schuchert (Zittel). 1913, p. 400. 



16. Buckman, 1910, p. 11. 



17. Hutton, 1905, p. 480. 



