Page:Pocock, The Scottish Silurian Scorpion.pdf/14

 branch. In  also there are two branches, the inner slender and unsegmented, the outer stout and composed of two principal segments. Although in general form the inner lobes (end., Pl. 19) of  resemble those of , they differ from the latter, and approach those of   in being unsegmented. The outer branch is broad and flattened, and is somewhat like that of, except that it is relatively smaller, and lies with its axial line directed, not longitudinally, but obliquely outwards and backwards like the comb of a typical scorpion. It shows, however, no signs of segmentation into so-called "fulcra" and "intermediate lamellæ," such as are found in the combs in the majority of species. Structurally, in short, it is intermediate between a typical comb and the outer branch of one of the mesosomatic appendages of. Furthermore, tho fine striæ which fringe its posterior edge are, in my opinion, too delicate to be the remains of teeth comparable in shape and size to those of recent scorpions. Rather would I suggest that they are portions of the edges of branchial lamellæ which were affixed like those of  to the posterior side of the appendage, with their lines of attachment lying at right angles to its longitudinal axis.

These appendages overlie and almost completely conceal the sternite of the third mesosomatic somite. The sternites of the fourth, fifth, and sixth somites, however, are fully exposed and well preserved. They are granular, and resemble the corresponding plates in recent scorpions but for the absence of the muscular impressions and, so far as my observations go, of the stigmata. Peach, however, declares most emphatically that "all four sterna exhibit on the right side undoubted slit-like stigmata at the usual places." It is true that the sternites are somewhat wrinkled laterally, and, as shown on Pl. 19, exhibit certain shallow impressions, which, especially in the case of the fourth and fifth sternites, might be mistaken for stigmata; but it is hard to believe that slits as conspicuous as the stigmata of recent scorpions should be so indistinctly preserved on sternites in such an