part 3] THE TEIAS OF IS'EW ZEALAND. 225 



the idea that the Mount-Potts Beds were of Permian age, an 

 idea further supported by the supposed occurrence of Glossopteris 

 in these beds. 



Spieifeeina otamitensis, sp. nov. (PL XXIV, figs. 9« & 9 J.) 



Both valves are about equally convex and slightly inflated. The 

 hinge-line represents in some examples the greatest, in others 

 nearly the greatest, width of the shell. The ventral beak projects 

 but slightly above the hinge-area. The ventral area extends the 

 whole length of the hinge-line, is moderately high, concave, and 

 faintly striate parallel to the margin. The delth^aium is open and 

 sunken, and the arrangement of dental plates and median septum 

 is cyrtiniform. In one specimen the apex of the ventral valve is 

 considerably thickened by a deposit of shelly matter. 



The anterior and lateral margins are gently rounded, the outline 

 forming more or less a semicircle. The dorsal valve has a rounded, 

 gradually-widening, median fold, with four lateral folds on each 

 side decreasing gradually in size. The median and the first two 

 lateral folds extend to the beak, but the last two lateral folds 

 die away before reaching it. The ventral valve has a rounded, 

 fairly-deep median sulcus, bounded on each side by five rounded 

 narrow folds graduall}^ decreasing in size, the last two of which 

 are very faint and do not reach the beak. The growth-lines are 

 well marked. 



Length =: 20 mm. ; width = 27 mm. 



Locality and horizon. — Bed <?, Otamita, Hokonui Hills, 

 with HalohicB of the group of H. zitfeli. I collected several 

 specimens bearing the shell, but they are more or less crushed or 

 flattened in the shale. 



Remarks. — This species belongs to the Sp.-iincinata group 

 of the DimidiatfE, but differs from Sp. nelsonensis and Sj:). 

 cf. austriaca in having a much narrower hinge-area and a less 

 prominent ventral beak, and also from the former in the absence 

 of a vertically-sulcate areal portion on each side of the delth^a-ium. 



Spieifeeina suessi var. austealis, nov. (PL XXIV, figs. 

 18«-14.) 



1882. H. Zugraayer, ' Untersuchuugeu iibev Rliatische Bracliiopoden ' p. 29 & 

 pi. iii, iigs. 14-19. 



The ventral valve is semip3a-amidal in shape, and more or less 

 semicircular in outline. The ventral area is almost vertical, 

 triangular, wider than it is high, tlat or ver}^ slightly concave, 

 and faintly striate parallel to the hinge-area. The ventral beak 

 scarcely projects above the area ; the delthyrium is triangular and 

 deeply sunken ; on each side of it a very narrow triangular area 

 is marked of£ and slightly sunken, and is faintly furrow^ed longi- 

 tudinally. In casts of the ventral beak the single incision of the 

 median septum is seen extending forwards for about a third of 

 the length of the valve. 



The surface of the ventral valve bears a deep, angular, rapidly- 



