There would doubtless be a just feeling of pride and satisfaction in the heart of a naturalist who could say that he had made himself thoroughly acquainted with all the species of a particular group of animals, had learned their most secret habits, and mastered their several relations to the objects, animate and inanimate, which surrounded them. But perhaps a still keener pleasure is enjoyed by one who carries about with him some problem of the kind but partially solved, and who, holding in his hand the clue which shall guide him onwards, sees in each new place that he visits fresh opportunities of discovery. The latter is certainly the condition of those who take an interest in searching out the habits and characters of trap-door spiders; for this subject, far from being exhausted, expands under the light of recently acquired facts, and invites research in many parts of Europe, north as well as south. We have only to compare the number of types of trap-door nest which were known before the publication of _Ants and Spiders_, with those at present recorded, to see how fruitful this field of inquiry has already proved. Before this little work was published, only one type of trap-door nest was known in Europe: two new types were described in its pages, and I have now the pleasure of being able to bring three more hitherto unknown European types before the notice of my readers, thus raising the number to six in all. I do not include in these six types the very curious, and still imperfectly-known nest of _Atypus_;[122] a spider which is a true representative of the trap-door group as far as its structural characters are concerned, but which, although it excavates a silk-lined burrow in the earth, does not appear to construct any kind of door at the mouth of its tube. [Footnote 122: See _Ants and Spiders_, page 78. _Atypus_ belongs to the sub-family _Atypinæ_, a division which does not include any of the _Nemesias_ or _Ctenizas_, and of which indeed _Atypus_ is the only European representative.] Much uncertainty still hangs over the habits of this spider, as the facts hitherto recorded, though perfectly authentic, are difficult to piece together into a satisfactory whole. One thing, however, is clear, and that is, that the nests and habits of the spiders of the genus _Atypus_ (of which, as Mr. Pickard-Cambridge, informs me, two if not three distinct species inhabit England) merit attentive study, and would most certainly repay it. Hastings, Portland, the coast of Dorsetshire, and the neighbourhood of London and Exeter, are the habitats hitherto cited for this spider, but I cannot doubt its existence in many sheltered localities on the south coast of England. The most recent contribution to our knowledge of this genus is contained in a paper by M. Eugène Simon,[123] who describes three species (two of which are new), as inhabiting France, and it remains to be ascertained whether our British _Atypi_ agree in their characters with any of these.