236 Transactions. 



The Age of the Hampden Beds. 



The main features of the Hampden beds were described in a former 

 paper, in which a brief reference w^as made to their geological position* 

 and to the opinions that had been expressed in regard to them by various 

 geologists. Further collecting has been done and a more complete examina- 

 tion of the specimens has been made since then, with the result that eight 

 additional species can now be recorded from these beds. Of these eight 

 species only one is Eecent ; thus the percentage of Recent species is only 

 slightly affected, and remains at 10-3. 



The specimen which was previously classed as Malletia sp. is now foimd 

 on examination of some perfect examples to be a new species of Sarepta. 

 It is much larger and has a much thicker shell than any other species of 

 Sarepta that has been previously recognized in this country. 



One of the additional species is Sfriithiolaria minor Marshall, which has 

 previously been recorded from Wangaloa only. Further examination of 

 Trigonia sp. shows that although it has an area with a sculpture quite 

 different from that on the rest of the shell, and is thus in no way related 

 to the Recent or Tertiary species of Trigonia, it yet apparently has teeth 

 that are destitute of the striations which are so characteristic of this genus. 

 Mr. Suter advised that it should be sent to England for further comparison 

 and examination. 



The specimen previously classed as Papijridea sp. is now found to be 

 certainly not a species of that genus, and in fact it is quite clear that it 

 does not belong to any genus that has hitherto been recognized among the 

 Recent or Tertiary species of Mollusca of New Zealand. Mr. Suter con- 

 sidered that it was a Pteriid, and suggested that it might belong to Pseudo- 

 monotis. The shell has a marked nacreous lustre, while its dentition suggests 

 a relationship to the species classed as Trigonia areolata Marshall, and its 

 ornamentation has no marked resemblance to any New Zealand genus. 

 It is here provisionally classed with the genus Trigonia. Mr. Suter remarked 

 that it was not possible to do justice to this species in New Zealand, where 

 comparatively little literature was available and few specimens from other 

 parts of the world were available for comparison. 



An additional specimen of Dicrolonia was obtained, but unfortunately 

 it also is incomplete ; but in the matrix in which it is embedded there are 

 definite impressions of the wings, and the species is now placed in the genus 

 Dicroloma wdth some confidence. It is most unfortunate that so many of 

 the species that are found in this locality should be in such a poor state 

 of preservation. 



The list of species that have been found at Hampden given above shows 

 that altogether some sixty-eight species have been obtained. Of these as 

 many as twenty-nine — a percentage of 42-7 — are regarded as new. This 

 very large proportion in itself suggests that the beds belong to an horizon 

 from which little collecting has been done in New Zealand. Since nearly 

 one thousand species of Mollusca have now been recorded from the Tertiary 

 rocks of this country, it is clear that the Hampden beds cannot be one of 

 the ordinary Tertiary horizons, from nearly all of which fairly large collec- 

 tions have now been made. 



Of other Hampden species that have also been found in other localities 

 the following are noteworthy. Gilhertia tertiaria Marshall is thought by 



*P. Marshall. Trans. N.Z. Inst., vol. 49, p. 463, 1917. 



