NO. 5 RHYNCHONELLOID BRACHIOPODS — COOPER 49 



Comparisons. — This genus was hitherto placed under Tegulorhyn- 

 chia and was generally regarded as the reference species for that 

 genus because it is a Recent as well as fossil form, the interior details 

 of which are well known. Significant differences between this and the 

 type species of Tegulorhynchia make it impossible to keep the two in 

 intimate association. The exterior ornamentation of the two is quite 

 distinct, Tegulorhynchia having the strongly squamose or spinose ex- 

 terior whereas Notosaria is costellate but with only fine growth lines. 



Another exterior difference of importance is the presence in No- 

 tosaria of disjunct deltidial plates. Tegulorhynchia has conjunct 

 deltidial plates and an entire foramen. Inside the pedicle valve the 

 pedicle collar of the modern form is not well developed. A major 

 difference appears inside the brachial valve of Tegulorhynchia. In 

 that genus the median septum extends posteriorly to unite with ex- 

 tensions from the crural base to form a thickened plate at the pos- 

 terior. This is illustrated by Chapman and Crespin (1923) for 

 T. coelata, plate 12, figure 17. In shells of modern Notosaria the 

 median septum is not extended to the apex. 



Geological horizon. — Miocene to Recent. 



Distribution. — New Zealand and Kerguelen Island; Belgium. 



Assigned species: 



Rhynchonella nigricans Sowerby, Miocene to Recent, New Zealand. 



R. nigricans pyxidata Davidson, Recent, Kerguelen Island. 



R. nysti Davidson, Pliocene, Belgium. 



Heinithyris sublaevis Thomson, Miocene, New Zealand. 



Discussion. — It may come as a surprise that the group of shells 

 so long associated under the generic name of Tegulorhynchia could 

 be separated, but the differences in ornamentation, beak characters, 

 and cardinalia are sufficient. The interior differences of significance 

 are in the pallial markings and cardinalia. 



As indicated on plate 6, B, figures 12 and 14, the pallial markings 

 in both valves of Notosaria are entirely different from those figured 

 by Leidhold (1922, pi. 11) for Tegulorhynchia doderleini (this 

 monograph pi. 22, C, figs. 16 and 17). In Notosaria the vascula media 

 cannot be easily distinguished on the inner shell surface and the 

 pallial marks make numerous short trunks extending anteriorly and 

 anterolaterally from the muscle and ovarian fields. The latter is also 

 not distinctly impressed but seems to be a quite narrow crescent in 

 the pedicle valve but somewhat wider in the brachial valve. The 

 pallial trunks of Tegulorhynchia as figured by Leidhold are like those 

 common to many other genera illustrated herein. 



