After reading a short piece on the Henri Barbusse book Stalin: A New World Seen Through One Man (originally published in French under the title Staline), I decided to buy a cheap copy through AbeBooks.com.  Earlier this week, I received the book in the mail.  It's a 1935 copy and apparently a first printing of the English edition.  Late last night, I decided to have a quick preview of the text before bed and a particular photo caught my eye.  The photo is a black and white plate opposite page 62 of the text.  Eight men are depicted in the image, but the caption only names seven of them:

Stalin and friends

click on the picture to view a larger image
As noted in the caption, the following men are clearly identified:

Above -  Avel Enukidze, Kliment Voroshilov, Lazar Kaganovich, and V. V. Kuibyshev
Below -  Sergo Ordzhonikidze, Josef Stalin, and Vyacheslav Molotov

Kirov
Sergei Kirov
The eighth man (to the right of Molotov) is obviously Sergei Kirov, who was murdered in 1934, around one year prior to the publication of the Barbusse book.  Despite the fact that Kirov's murder was a monumental event in the early history of the USSR – one with resounding consequences and enduring controversy for many years to come – Kirov's name is clearly missing from the caption, replaced with periods of ellipsis.  There are no clues in the immediate text as to the basis for the omission. Kirov is mentioned (with the old spelling "Kiroff") much later in the text on pages 114 and 181, but these are merely fleeting references to his assassination with no indication as to Kirov's prominence before death nor as to the significance of his assassination relative to the political climate of the time.

I'm sure I'm not the first person to have noticed this peculiarity, but I must say for posterity that this certainly is a curious omission, indeed.
Further Reading
Stalin in Reality and Legend by Walter Held (1935 book review of Staline by Henri Barbusse)