50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



The cardinalia of the two genera are similar except for the median 

 ridge. In Notosaria the median ridge is short and thick and is usually 

 on a small callosity between the posterior adductors. The ridge does 

 not extend to the apex which is generally smooth. In Tegulorhynchia 

 on the other hand the median septum is short but extends to the apex 

 where it meets short extensions from the crural bases which form a 

 small apical callosity. The cardinal process of Notosaria is well de- 

 veloped but that of Tegulorhynchia can scarcely be distinguished. 



Rhynchonella nysti Davidson from the Pliocene of Belgium was 

 referred by Thomson (1927, p. 154) to Tegulorhynchia with the re- 

 mark that Davidson (1874a, p. 7) had compared the species to 

 Tegulorhynchia nigricans. Comparison of the interior and exterior 

 details corroborates this assignment and comparison. The beak 

 characters of a pedicle valve in the national collection (U.S.N.M. 

 549417a) has the characteristic foramen and deltidial plates of No- 

 tosaria. The cardinalia, too, are like those of Notosaria as shown 

 by a brachial valve (U.S.N.M. 549417b). The sockets are large 

 and the socket plates broad and strong. The cardinal process is a 

 thickened triangular callosity like that of the New Zealand species. 

 These features combined with the exterior ornament clinch the as- 

 signment. Rhynchonella nysti is costate and the costae bifurcate at 

 places on the valve as in the New Zealand shell, a feature unusual in 

 the Rhynchonelloidea. This occurrence, as Thomson remarks, leads 

 to interesting speculation on the paleogeographic distribution of 

 Notosaria. It is possible that the Austral members of the genus 

 originated in European waters and thus constitute a clearly distinct 

 stock from Tegulorhynchia as its anatomy suggests. 



Genus TEGULORHYNCHIA Chapman and Crespin, 1923 



Plates 5, D, 21, E 



Tegulorhynchia Chapman and Crespin, Proc. Roy. Soc. Victoria, n. s., vol. 35, 

 pt. 2, p. 175, 1923; Thomson, New Zealand Board Sci. Art, Manual 7, p. 

 152, 1927. 



Transversely triangular to subpentagonal in outline; inequivalve, 

 the brachial valve having the greater depth ; anterior commissure 

 rectimarginate, the brachial valve having a moderately well-defined 

 fold ; surface costellate and lamellose, the lamellae being produced 

 into hollow spines in some species. Beak of pedicle valve long and 

 pointed; foramen complete in the type of the genus (Allan, 1940, 

 p. 279) . large, hypothyrid ; deltidial plates usually conjunct. 



Pedicle valve interior with strong corrugated teeth supported by 



