.part 3] THE TKIAS OF XEW ZEALAND. 231 



Spieigeea weeti Zittel. (PI. XXY, figs. 6 « & 6 h.) 



1864. ' Palaoutologie von Xeu-Seeland ' p. 23 & pi. viii, figs. 3 a-3 d. 



Zittel, when lie described it, had only casts of this species, which 

 Hochstetter collected in the Xelson district. I therefore take the 

 opportunity of describing and illustrating a fine uncrushed testi- 

 ferous example, which I found in a pebbly felsi^athic grit on the 

 western slope of Mount Heslington. It is rather wider than long, 

 the ventral valve is rather inflated, the dorsal less so. The ventral 

 beak is comparatively small ; the area is narrow and faintly striate 

 parallel to the hinge-margin ; the delthyrium is triangular and deeply 

 sunken, and only slightl}^ hidden by the dorsal beak. The apex 

 is perforated by a pedicular foramen of moderate size. The ventral 

 valve has a broad, shallow, median sulcus which dies away about 

 halfway to the beak, and two faint lateral sulci which only appear 

 near the anterior lateral margins. The dorsal valve bears near its 

 anterior margin a broad median fold, which is bordered by steep 

 slopes. It measures 28 mm. in length, 31 mm. in width, and 

 16 mm. in thickness. The gro^^i:h-lines are well marked. 



L oca lit 3^ and horizon. — This is a common Carnic fossil in 

 New Zealand : it occm-s at Mount Heslington and in the Wairoa 

 Gorge ; in the Hokonui Hills ; at Nugget Point and other places 

 in the South Island. It is also reported to occur in New Caledonia. 



Remarks. — Zittel mentions the large cardinal process, and 

 Bittner remarks upon the resemblance of this shell to the Alpine 

 lihtetic Spirigera oxycoJpos. 



I have employed the generic name Spirigera (A. d'Orbigny, 

 1817) in preference to Atliyris (McCoy, 1811) for the Triassic 

 forms of this group, in conformity with the writings of Zittel, 

 Bittner, Diener, and others, by Avhom it is used so largely. 

 The name Spirigera seems to be coming into use to designate the 

 Mesozoic Athyrids. 



Spieigeea kaihikuaxa, sp. nov. (PI. XXY, fig. 5.) 



Shell rather inflated, the ventral valve slightly more than the 

 dorsal. Outline elongate-oval or subtriangular, often Avidening 

 out towards the anterior margin, which is genth^ rounded. The 

 ventral beak is prominent, and tapers graduall}'. The delthyrial 

 cavity is more or less entirely concealed by the dorsal beak. The 

 foramen was wide and remained open during life, as the casts are 

 always attached to the interior of the cavity by rock which filled 

 up the foraminal passage : this, in some examples, is extended 

 forward, and encroaches on the delthyrium. 



There is a faint broad fold on the anterior part of the dorsal 

 valve, and a very faint corresponding median depression on the 

 ventral valve : consequently, the junction of the valves lies almost 

 in one plane. The ventral apical region is much thickened at the 

 sides with shelly material, but a passage for the pedicle-muscle 

 alwavs remains. 



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