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Show 460 MESSRS. BLACKMORE AND ALSTON [June 16, I published m y account of this singular species in the 'Ibis' (1869, p. 304) several additional and interesting particulars have been added to its life-history by M r . Potts (Trans. N . Z. Inst. vol. iii. p. 93) and by M r . Buller (Birds of N e w 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. R. Cook, the collector above referred to, reports that he took the egg here figured with two others from a nest in the Otaio riverbed, 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 agyptius, p. 456. 3. Hoplopterus ventralis, p. 455. 4. Mgialitis pecuarius, p. 457. 5. tricollaris, p. 457. 6. falklandicus, p. 457. Fig. 7. Mgialitis collaris, p. 458. 8. ruficapillus, p. 459. 9. nigrifrons, p. 459. 10. Himantopus novce-zealandice, p. 459. 11. Anarhynchus frontalis, p. 459. 11. On Fossil Arvicolida. 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 information which we at present possess as to Arvicolida 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 characteristic 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 Arvicolida; and when taken along with other structural details and with external characters they afford an invaluable 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 |
