OGYGIA. 135 



Ogygia peltata, Salter. PI. XVII, fig. 8. 



Ogygia scutatrix, Salter. Siluria, 2nd ed., p. 53, Foss. 9, f. 1, 1859. 



— PELTATA, Id. Append. Ramsay, Geol. N. Wales ; Mem. Geol. Survey, 

 vol. iii, p. 313, pi. xii, fig. 8, 1866. 



0. modica, vel caput, thoracem, caudam csqualis. Glabella lata, lavis, sulcis nullis. 

 Thorax axe depresso, pleuris angustior ; his usque ad apices falcatos nee decurvos planis- 

 simis ; fulcro ohsoleto. Cauda quam semicircular i longior, axe lato S-annulato ; limbo 

 sulcis primariis subrectis, secondariis ahbreviatis. 



We have only portions of tliis fine species, but these enable us to reconstruct a fossil 

 certainly four inches in length, of a broad-oval shape. Our fig. 8 is a copy of the figure 

 in the ' Survey Memoir' above quoted. It is probably not of the full breadth, but nearly 

 so ; and I have no specimen which more completely shows the true shape. 



The head, thorax, and tail, are nearly of the same length ; the head is somewhat 

 longer than a semicircle, with very short broad head-spines. It is widely margined ; and 

 the glabella is well distinguished from the cheeks, and is of the same width with them, 

 parallel-sided, reaching five sixths the length of the head, and without any distinct lobes 

 except the neck-segment, which is strongly marked out. The eyes are large ?, placed half 

 way up the head. The portion of the neck- furrow beneath the cheeks is much nearer to 

 the posterior margin than that beneath the glabella, and abruptly so (see fig. 8). The 

 striated margin to the cheeks is very broad towards the front. 



Thorax with a wide axis, not quite so wide as the pleurae, and somewhat narrower 

 behind. The rings of the axis are very flat, and scalloped out at their junction with the 

 pleurae, so that the axal-furrows in this (as in the preceding species) present a set of 

 re-entering angles, with concave arches between them. The pleurae are flat, straight as 

 far as the fulcrum, which is placed at two thirds out. The pleural groove is sharp and 

 sigmoid in its curve, and reaches nearly to the falcate tip without any angular bend. It 

 is parallel to the front edge, apparently more so than in 0. scutatrix, and the hinder half 

 of the pleurae is rather the largest. 



The tail is a semicircle, the axis occupying rather more than a fourth of the entire 

 width, and tapering backwards for nearly three foiulhs of the length. It is annulated by 

 seven furrows, which, except the two or three last, stretch right across. The tip is blunt, 

 and rather obscure. The sides are radiated by eight strong grooves, including the upper 

 or submarginal one, which are all slightly bent downward near their ends, and are inter- 

 lined by similar but much shallower furrows, which start abruptly (as in the last species) 

 from a point near, but not close to, the axis. A plain smooth (?) border to the upper 

 surface, and the incurved fascia narrow and closely striated. 



The specimens described are all from the north-west angle of Whitesand Bay, St. 

 David's Head, and difier from the N. Welsh species last described as follows : — The form 

 more elongate ; the pleurae flatter, much shorter, and more pointed ; the tail with a 



