.

68. ,, ,, ,, PELLUCIDA.

CYRENIDAE.

69. Sphaerium corneum, _var._ COMPRESSUM.

70. ,, ,, ,, MINOR.

71. ,, ,, ,, STAGNICOLA.

72. ,, ovale, _var._ PALLIDUM. England.

73. ,, lacustre, _var._ ROTUNDUM. Wales.

74. Pisidium pusillum, _var._ GRANDIS.

75. ,, ,, ,, CIRCULARE. Wales.

76. ,, nitidum, _var._ GLOBOSUM.

{359} UNIONIDAE.

77. Unio tumidus, _var._ RICHENSIS. Regent's Park. Peculiar form.

78. ,, pictorum, _var._ LATIOR. England.

79. ,, ,, ,, COMPRESSUS. England.

80. ,, margaritifer, _var._ OLIVACEUS.

81. Anodonta cygnaea, _var._ INCRASSATA. England.

82. ,, ,, ,, PALLIDA. England, Ireland.

ESTUARINE OR MARINE PULMONOTRANCHS.

83. ASSIMINEA GRAYANA. Thames Estuary.

_Peculiarities of the British Flora._--Thinking it probable that there must
also be some peculiar British plants, but not finding any enumeration of
such in the _British Floras_ of Babington, Hooker, or Bentham, I applied to
the greatest living authority on the distribution of British plants--the
late Mr. H. C. Watson, who very kindly gave me the information I required,
and I cannot do better than quote his words: "It may be stated pretty
confidently that there is no 'species' (generally accepted among botanists
as a good species) peculiar to the British Isles. True, during the past
hundred years, nominally new species have been named and described on
British specimens only, from time to time. But these have gradually come to
be identified with species described elsewhere under other names--or they
have been reduced in rank by succeeding botanists, and placed or replaced
as varieties of more widely distributed species. In his _British Rubi_
Professor Babington includes as good species, some half-dozen which he has,
apparently, not identified with any foreign species or variety. None of
these are accepted as 'true species,' nor even as 'sub-species' in the
_Students' Flora_, where the brambles are described by Baker, a botanist
well acquainted with the plants of Britain. And as all these nominal
species of Rubi are of late creation, they have truly never been subjected
to real or critical tests as 'species.'"

In my first edition I was only able to name four species, sub-species, or
varieties of flowering plants which were believed to be unknown on