III.—On the Lobe-line of Certain Species of Lias Ammonites Described in the Monograph by the late Dr. Wright

Extract

While recently turning over the plates of this Monograph, my attention was arrested by the lobe-line figured on plate 63, and on looking at the explanation of the plate given on the opposite page, I was much surprised to see that it was stated to be the “Lobe-line of Harpoceras ovatum, magnified.” On the same plate, just below (fig. 4) is a side view of the Harp, ovatum with its lobeline in situ, and I suppose it to be this lobe-line that is magnified. But there must surely be some mistake here. Compare the lobeline, fig. 7, with that on fig. 4, and notice the much greater width of the siphonal saddle in fig. 4 (than in fig. 7), where, on account of the curvature of the fossil, it would be really smaller. To say nothing of the obliquity of the inner portion of that on fig. 4, where is the first auxiliary lobe (nearly as large as the inferior lateral in fig. 7) to be found in fig. 4? I think it will be apparent that for some reason or other the two lobe-lines are different. But is the lobe-line, fig. 7, the correct lobe-line for such a species as the Harp, ovatum here figured? I must say No! Turning for a moment to Wright's description of the lobe-line of Harp, ovatum, page 446, we find it stated, “The suture-line is of the radians type.”