part 3] THE TEiAS or i^^ew zealai^d. 217 



Caroline Cutting in the Hokonui Hills. It persists into the 

 Carnic beds, but becomes much scarcer. 



Kemarks. — I think that this shell should be placed in Bittner's- 

 group Halorella, although the dorsal median sulcus is rather flat- 

 tened than sunken. In outline it recalls H. fedata var. coarcfata 

 Bittner of the Alpine Trias, but in that form the ribs continue 

 from the anterior margin to the beak. 



Haloeella sp. (PI. XXIII, fig. 4.) 



A single fragmentary dorsal valve has a very faint median sulcus- 

 and about twent}^ ver}" regular ribs, all of about equal height. The 

 sulci between the ribs are of equal depth. The lateral ribs become 

 curved as they approach the anterior lateral margins, and all ribs 

 extend to the beak region. There is a short median dorsal septum. 



Locality and horizon. — Eighty-Eight Valley, Xelson. Ap- 

 parently from the Mytiliis-^^rohlematiciis Bed. New Zealand 

 G-eological Survey Collection. Carnic. 



Be marks. — This Halorella belongs to the group of H. pedafa 

 Bi'onn and H. ampltitoma Bronn. It seems to agree best with 

 H. pedata var. multicostata, ^\hic\\ has twenty Or twent^^-f our ribs. 

 These forms occur in the Alps in the Hallstatt andDachstein Beds. 

 J. Wanner 1 records a very similar variety of H. ampliifoma, with 

 about eighteen ribs, from North- Eastern Serang in the Malay 

 Archipelago. 



Dielasma cf. himalata:^a Bittner. 



1899. ' Trias Bracb. & Lamellibrancli.' Pal. lud. ser. 15, vo\ ii', pt. 2, p. 25 &• 

 pi. V, figs. 1-8, 10, 11. 



Small forms of rounded or oval outline occur plentifull}" as 

 casts in the lower strata of the New Zealand fossiliferous Trias. 

 The shell bears none or only a very faint plication, and gutta-percha 

 squeezes show that the growth-lines are closely set and well 

 marked. The dental plates of the ventral valve and the median 

 septum of the dorsal valve are well developed. 



They are generally of small size, and are not strongly inflated : 

 one specimen is 11 mm. long and 10 mm. wide. 



Locality and h o r i z o n . — This form is plentiful in the Kaihiku 

 Beds at Caroline Cuttuig and other localities ; and I found casts of 

 this or a ver}'^ similar small Dielasma in the Halohia Beds at 

 Mount Heslington, but they become very scarce in the Carnic. 



Remarks. — This form recalls the Permian D. elonc/afa Schlot- 

 heim, but I think that it is identical with D. lihnalai/ana 

 Bittner, which occurs in the main complex of the Muschelkalk and 

 in the beds with Spiriferina sfracheiji Salter in the Himalayas. 



Dielasma zealajS'dica, sp. nov. (PL XXIII, fig. 5.) 



Shell elongated, the outline tapering gradually towards the beak,, 

 but expanding towards the anterior margin, which is well rounded. 



1 Bibliography, 49, p. 187 & pi. vii, fig. 8. 



