"31. English and French surnames beginning with a prefix (except the French De and D') are to be recorded under the prefix; in other languages, under the word following."
The British Museum rule stands thus:—
"12. Foreign names, excepting French, preceded by a preposition and article, or by both, to be entered under the name immediately following. French names preceded by a preposition only, to follow the same rule: those preceded by an article, or by a preposition and an article, to be entered under the initial letter of the article. English surnames, of foreign origin, to be entered under their initial, even if originally belonging to a preposition."
The Cambridge rules are as follows:—
"8. German and Dutch names, preceded by a preposition or an article, or both, to be catalogued under the name, and not under the preposition or article.
"9. French, Italian, Spanish, and Portuguese names, preceded by a preposition only, to be catalogued under the name; those preceded by an article, or by a preposition and an article forming one word, to be catalogued under the article or combined preposition and article."
The point was fully considered by the Index Society; and as the rule laid down by the Council is full and clear, I venture to give it here in addition to those above.
"5. Proper names of foreigners to be alphabetically arranged under the prefixes
| Dal. | as | Dal Sie. |
| Del. | Del Rio. | |
| Della. | Della Casa. | |
| Des. | Des Cloiseaux. | |
| Du. | Du Bois. | |
| La. | La Condamine. | |
| Le. | Le Sage. |