part 3] THE TRIAS or NEW ZEALAND. 235 



This genus comprises a well-defined group of specialized bi- 

 :sulcate Spirigerids, which shows close relationship) to /S'^j>. oxycolpos 

 of the Alpine Khsetic in the structure of the cardinal process and 

 the deepened pit beneath it. They differ, however, in features 

 .sufficiently marked to justify their attribution to a new genus or 

 subgenus, such as the equal convexity and equal median sulcation 

 in both valves, the greater internal posterior thickening of the 

 valves,- and the relatively-larger size of the cardinal process. 



Locality and horizon. — Two species appear to occur in the 

 Trias, and one in the Jurassic, of New Zealand. They are rather 

 scarce in the Carnic of the Hokonui district ; but they occur in 

 great abundance in some beds of E-haetic age, and a single rather 

 dwarfed form survives into the Jurassic. 



Remarks. — Hector proposed the generic name Clavigera for 

 this group, in a paper read before the Wellington . Philosophical 

 Society in 1878. An abstract of this paper was published the 

 following year, but it never appeared in full. Some plates which 

 he caused to be printed about that time have recently been issued 

 with a palseontological bulletin already mentionecl.^ PI. i is 

 occupied by illustrations of the genus Clavigera. Some years ago 

 Mr. McKay collated these plates, and labelled the species so far 

 as he could from memory: he gave the species on pi. i as follows: 

 Clavigera hisulcata., CI. cuneiformis., CI. gracilis, CI. tumicla, 

 and Gl. 'sp. innom.' I have adopted the specific names hisiilcata, 

 tumida, and cuneiformis for the forms for which Hector appa- 

 rently intended them — the last name referring to the Jurassic 

 shell. Clavigera gracilis is a cast from Benmore Cutting, 

 apparently identical with CI. tumida. Hector gave drawings of 

 CI. cuneijormis and of a cast of CI. tumida, but without any 

 specific names, in a work issued in 1886. ^ For reasons already 

 stated, I considered it advisable to discard Hector's name Clavigera 

 and to institute that of liectoria instead. 



Hectoeia bisulcata, sp. nov. (PI. XXV, figs. 1 « & 1 i.) 



Shell rather wider than long, moderately inflated, the valves 

 almost equally convex. The hinge-line is nearly straight, and 

 represents the greatest ^vidth of the shell. The area is narrow and 

 faintly striate parallel to the margin, and the ventral beak projects 

 slightly above the area. The delthyrium is triangular and in- 

 sunken. The growth-lines show that the outline of the young 

 shell was rather strongly alate ; but towards maturity it becomes 

 less so, and is more or less produced anteriorly. The outline main- 

 tains the same width at the sides for some distance from the 

 hinge-line, and then narrows to the anterior margin, which is gently 

 rounded. In both valves two raised rounded ridges diverge from 

 the beaks, and proceed towards the anterior margin meeting the 

 similar ridges of the opposite valve. They enclose a shallow, 



^ Bibliography, 47. 



2 Catal. Ind. & Col. Exhib. (1886) p. 72, figs. 2 & 3. 



