380 Transactions. 



A single specimen from the WeJca Pass stone at Onepmiga, though only 

 22 mm. in length, agrees closely in all external characters with the holotype, 

 and^ moreover, possesses the same fine texture of shell and the pale purplish- 

 brown colour which seems to be characteristic of this species. In the orginal 

 description the shell was described as suborbicular, but it is slightly more 

 elongate than this, and perhaps more correctly described as broadly ovate. 



P. huttoni occurs commonly in the Waitaki limestone at Maerewhenua 

 and Ngapara, and is also known from the greensands at the base of the 

 Maerewhenua limestone and the greensands overlying the Wharekuri lime- 

 stone. 



Pachymagqs andrewi Series. 



Pachymagas andrewi n. sp. (Plate XXVI, figs. 1, 2.) 



Shell broadly ovate, beak short, acute, hinge-line narrow, acute, sides 

 convex and rounded, front slightly produced, rounded. Valves moderately 

 convex, ventral valve with a broad rounded fold and slightly flattened 

 sides, dorsal valve reflected anteriorly, anterior commissure with a broad, 

 fairly deep ventral sinuation, not completely flattened along the bottom. 

 Beak erect, slightly produced dorsally of the hinge-line, foramen small, 

 mesothyrid, attrite. Cardinal process large and swollen, comparable to 

 that of Neothyris ovalis. Length of holotype, 46 mm. ; breadth, 44 mm. ; 

 thickness, 21 mm. (estimated). The ventral valve of the holotype is damaged, 

 but the folding of this valve is well shown on a paratype. 



This species differs from all the preceding in the smallness of the fora- 

 men. It may conceivably belong to Neothyris and not Pachymagas. It 

 differs from P. huttoni in the absence of the carination of the beak. In its 

 small foramen it agrees with Terebratella lahillei Ihering, a species com- 

 pared by its author with Pachymagas venter, and perhaps a member of 

 that series, but it is more elongate and broadly oval instead of suborbicular. 



Type locality : Creamy calcareous sandstone immediately succeeding 

 the main Mount Brown limestone, foot of dip-slope of the latter, Weka Pass. 

 The species is rare in the type locality, and not recognized elsewhere. 



Genus Waiparia n. gen. 

 Genotype, Pachymagas abnormis Thomson. 



A genus of the Terebratellidae with a septum showing the remains of 

 transverse bands, and therefore presumably with a loop of the Terebratelli- 

 form pattern. Rostrum subapicate, foramen submesothyrid, having just 

 left the hypothyrid position, deltidial plates conjunct — i.e., united between 

 the foramen and the dorsal umbo. In these characters the genus differs 

 from Pachymagas and Terebratella, in which the rostrum is trmicate and 

 the foramen mesothyrid. Cardinalia simil^'r to those of young specimens 

 and primitive species of Pachymagas, with strong socket-ridges but a slender 

 septum, a hinge-trough with flatly inclined walls and a small cardinal process 

 confined to the umbo. The bifurcations of the septum forming the anterior 

 walls of the hinge-trough overhang slightly outwards, and are thus more 

 excavate than is usual in Pachymagas, but much less so than the hinge- 

 plates of Terebratella. The teeth of the ventral valve rise from swollen 

 bases as in Pachymagas. 



This genus may be considered as springing from the same stock as Pachy- 

 magas, but lagging behind in foraminal evolution. It possibly gave rise 

 directly to Pachymagas of the type of P. ellipticus, which possesses a fora- 

 men which is submesothyrid but almost mesothryid. 



