12 12 HYRTA 



Schumacher's section h, {P. tntiicatits Scliiiin). Lea erred in 

 this, because Klein was not a binomial author, and his name 

 can not be used. In the Proceedings of ihe U. S. National 

 Museum, XMII, 1896, p. 315, I restored the name of Prisodon 

 Schumacher to the first section, pointing out that the P. ohli- 

 quus Schumacher must stand as its type. Two years after 

 Schumacher's name appeared Lamarck published the generic 

 name Hyria in the Animaux sans Vertebres, VI, 18 19, p. 81, 

 and placed in it first his H. aviciilaris, which equals Schu- 

 macher's P. obliquHs, and secondly H. corrugata. I now be- 

 lieve that these corrugated forms are generically distinct from 

 the smooth ones, and as Schumacher's Paxyodon is almost 

 certainly founded on one of the smooth species, Lamarck's 

 name Hyria can be used by eHmination for the corrugatus and 

 allied forms. 



Kry to sprcies of Hyria. 



Shell with radial pseudocardinals, H. stevensi. 



Pseudocardinals more or less longitudinal. 



Entire surface subradially sculptured, H. rugosissima. 



Later growth usually not radially sculptured. 



Triangular, earlier growth radially sculptured; later 



growth concentrically sculptured. H. latialata. 



Rhomboid, only a few strong umbonal ridges. 



H. transversa. 

 Subrhomboid, surface more or less radially sculptured. 



H. corrugata. 

 Subgenus Hyria s. s. 



Characters as in the genus. 

 Type, Hyria corrugata Lamarck. 



Hyria corri'Gata Lamarck. 



Shell subtrapezoid, convex or slightly inflated, varying from 

 almost thin to solid, inequilateral; beaks low, subcompressed, 

 sculptured with strong, subradial ribs, which usually converge 

 in front of the posterior ridge and are often divaricate along 

 it ; this sculpture often extends more or less over the disk 

 and occasionally becomes zigzag or subtiodulous ; posterior 



