Diplograptus penna Hopkinson 1869, and its bearing on vesicular structures W.D.V. Jones and R.B. Rickards Paläontologische Zeitschrift 1967, 41, 3/4, 173-185
A redescription of Diplograptus penna Hopkinson 1869 is given, based largely upon three-dimensional material. The significance of the discoveries is discussed with respect to the concept of Cystograptus Hundt 1942. The so-called "vesicles" of "Orthograptus" vesiculosus Nicholson and Diplograptus penna Hopkinson are interpreted as three vaned structures.