part 3] THE TEIAS OF IS^EW ZEALAND. 201 



nearest to H. ciusfriacn, which is a Carnic fossil and, in the 

 Austrian Alps, builds up banks in the limestones with BucepltaJus 

 suhbullafiis. The flattened ribs of irregular width and the sharph^- 

 cut furi-ows of the present form recall those of the 3^oung shell of 

 H. Iwchsfefferi ; but the beak in II. austriaca is less strongly 

 inclined forwards, also the ribs show no waviness and do not bend 

 forwards. 



Halobia spp. 



In addition to the three forms of Halobia already described, the 

 Carnic beds of the New Zealand Trias contain at least two other 

 smaller and less conspicuous formS; which appear to be distinctive- 

 and probably new species, although from the rather scanty nature 

 of the material obtained by me I hardly feel inclined at present to 

 record them as such. As they occur in the same bed at Otamita 

 and Mount Heslington as the forms just described, and as they 

 appear to be un described species, a description of them cannot add 

 any further information regarding the hoiizon of these beds than 

 that yielded by the forms which closeh^ resemble H. zitteli and 

 H. austriaca. I may remark, however, that a small Halobia, very 

 common in Bed c at Otamita, strongly resembles a shell which 

 Bittner illustrates under the appellation ' Halobia, n. sp., aft'. 

 neumayri Bittner,' from the Upper Trias of Balia in Asia Minor. 

 I do not recollect finding the forms allied to H. zitteli or 

 H. hochstetteri in Bed c at Otamita, and so the small Halobias 

 mentioned above may characterize a rather higher horizon. Halobia 

 neumayri, which occurs at Balia, is a species of the group to 

 which H. zitteli and H. Jioclistetteri belong. A careful and 

 prolonged zonal collecting of the Carnic Halobias of the New 

 Zealand Trias would probably yield further interesting results. 



MyTILTJS (?) PEOBLEMATTCUS Zittcl. (PL XX, fig. 8.) 

 1834. ' Palaontologie von Neu-Seeknd ' p. 28 & pi. viii, figs. a-h. 



Shell thin, mytiliform, the beaks anteriorly situated, terminal^ 

 the upper posterior margin bluntly alate. 



Area straight or slightly curved ; behind the beak is a concave 

 ligament-groove bearing faint parallel striae. I saw no trace o£ 

 hinge-teeth nor of muscle-scars. Some specimens seem to have 

 a small, narrow, b^^ssal sinus below the beak. There is a small 

 plate or septum inside the beak. A typical specimen measures- 

 109 mm. in length. The specimen illustrated is a small left valve. 



Locality and horizon. — The Mytilus-problematicus Bed 

 forms a very constant horizon about the middle of the Carnic in 

 all the principal sections in the South Island. It has not been 

 traced in the North Island, but reappears in New Caledonia. The 

 bed is made up of incredible quantities of separated valves, among 

 which an occasional valve of Holtonuia, or of the form next to be 



