460 



MESSRS. BLACKMORE AND ALSTON 



[June 16, 



I published my account of this singular species in the 'Ibis' (1869, 

 p. 304) several additional and interesting particulars have been added 

 to its life-history by Mr. Potts (Trans. N. Z. Inst. vol. iii. p. 93) and 

 by Mr. Buller (Birds of New Zealand, p. 216). 



The egg, however, has not hitherto been figured ; and the following 

 notes, by the collector, will doubtless be acceptable to ornithologists. 

 Mr. J. It. Cook, the collector above referred to, reports that he took 

 the egg here figured with two others from a nest in the Otaio river- 

 bed, Canterbury Settlement, on the 20th October, 1872. The nest 

 was on sand amongst shingle, and very hard to find, although the 

 birds were bold. The eggs were placed point downwards and were 

 almost covered with small pieces of lichen, apparently placed there 

 by the bird for the purpose of concealing them during its absence 

 from the nest. 



EXPLANATION OF PLATE LX. 



Fig. 1. Glareola lactea, p. 455. 



2. Pluvianus mgypUus, p. 456. 



3. Hoplopterus ventralis, p. 455. 



4. JEffialitis pecuarius, p. 457. 



5. tricollaris, p. 457. 



6. falklandicus, p. 457. 



Fig. 7. Mgialitis collaris, p. 458. 



8. ruficapillus, p. 459. 



9. niffrifrons, p. 459. 



10. Himantopus nova-zealandice, 



p. 459. 



11. Anarhynchus frontalis, p. 459. 



11. On Fossil Arvicolidce. By Humphrey P. Blackmore, 



M.D., and Edward R. Alston, F.Z.S. 



[Eeceived June 10, 1874.] 



In the following pages we have attempted to review the informa- 

 tion which we at present possess as to Arvicolidce that have been 

 found in a fossil state, and their relationship to recent species. In 

 the course of our investigations the conclusion has been forced upon 

 us, that in many cases it is not possible to identify and define species 

 of this family by the pattern of the molar teeth alone with the 

 accuracy which has been claimed ; and as these are the only cha- 

 racteristic remains which are forthcoming in the case of most of the 

 fossils, it follows that some of our determinations are and must be 

 merely approximate. 



Blasius seems to have been the first to recognize the diagnostic 

 value of the form and number of the prisms which form the crowns 

 of the molars in the Arvicolidce ; and when taken along with other 

 structural details and with external characters they afford an in- 

 valuable key to the numerous species and varieties of this most 

 difficult group. But when considered alone they are not conclusive 

 in every case. Thus, for example, A, arvalis cannot be separated 

 by its teeth from the very distinct A. subterraneus, while many 

 species are liable to occasional individual variations which might 

 well be regarded as showing specific distinction if other characters 

 were overlooked. Again, the form and proportions of some of the 

 bones of the skull vary very considerably according to the age of 

 the animal — a fact which has been overlooked by many writers 



