14 Description of Genera and Si^ecies. 



into an elongated tlattened plate, which is somewhat indented in the mid-line, and is 

 corrugated radially and set with strong bristles round its hinder margin. The anterior 

 part of the telson, at a short distance from the articulation, developes a median furrow 

 which divides the tumid portion into two areas and is carried back to the constricted part. 

 From behind each tumid area there is continued a ridge surmounted by a keel which, 

 diminishing as it passes backwards, terminates at the angle made by the constriction. 

 The external edge (fig. 3) of this part of the telson is fringed with strong and longish, 

 even-sized bristles which show no tendency to have recurring finer and stronger 

 filaments, as in Gnathophausia. Several specimens (figs. 1, 3, 5) show that flattened lobes 

 fringed with setaj were articulated with the telson at its constriction, which evidently 

 assisted in forming the tail fan, like those shown in the American Anthrajmhvmov 

 gracilis^ of Meek and Worthen. With the exceptions above mentioned, the telson of 

 this species is constructed on almost identical lines with that of Gnathophausia. The 

 terminal lobe appears to be a feature of the ancient Lophogastrids as it occurs in other 

 genera, as will be shown in the sequel. 



The eye (figs. 1, 3, 4, 7, 7a) is large and nearly always directed outwards. The 

 stalk is very narrow at the base, and after an articulation it suddenly expands into a 

 cup-shaped pedicle, the margin of which is always undulating and so often notched at 

 the same place in different individuals when crushed that the cornea appears to have 

 been slightly pear-shaped or lobed. In a great manj' specimens there has been observed 

 a projection proceeding from the outside of the pedicle on the side of the eye next the 

 rostrum. In fact, it is invariably to be observed if the eye is sufficiently well preserved 

 the right way up to show it. There can be no doubt that it represents the ocular 

 papilla, the relic of a temporary functional larval eye such as appears in Gna.tho]>hausia 

 and other Schizopods In the present species it is moderately large compared with the 

 size of the eye. and is bent round and directed forwards (figs. 4, 7^^). The antennules (figs. 

 1, 3, 4, 5) consist of a massive elongated three-jointed peduncle measuring over 5 mm., 

 the last joint of which is ridged along its inner margin and well set with settv, and 

 extends beyond the tip of the rostrum. This joint gives offtwo stout, but comparatively 

 short, fiagella a little longer than the peduncles, the inner flagellum being somewhat the 

 stouter and longer, in this respect differing widely from the recent Lophogastrids in whicli 

 this branch of the antennules is more massive than the fiagellum of the antenna. The 

 specimens are not sufficiently well preserved to show whether the peculiar scale-like 

 sensory organ that is found between the bases of the fiagella occurs in this species or 

 not. In nine cases out of ten the terminal joint of the propodite is pre.ssed against the 



'0('ol. Svirv. Illinois Report, 1S66, vol. 1, \\. 407, pi. .\.\xii, fig. 4 a.b.c. 



