
TRANSACTIONS OF THE SECTIONS. 59 
On a few Genera of Irish Silurian Fossils. 
By J. W. Sater, F.G.S., of the Government School of Mines. 
CrusTAcEA. 
Among the many new and interesting forms of Trilobites described by Colonel 
Portlock in his work on Londonderry and Tyrone, a small species of Asaphus was 
recorded from the Lower Silurian of Tyrone, which he named 4. /atifrons, distin- 
guishing it from some other species by the breadth of front included within the curve 
of the facial suture. The species is very remarkable for the position of the eyes, 
which are placed very far backward and inward, so as to be close to the base of the 
small and narrow glabella. This peculiarity of habit is associated with some other 
characters which will remove the species from Asaphus, to which, nevertheless, it is 
closely allied. It has also some relations with I//enus. 
Stygina, new genus. 
Gen. Cuan. Body ovate and rather flattened. “Head and tqil large and tolerably 
equal, body of 9 rings. Eyes small, placed far backward and inward, near the 
base of the glabella, which is quite indistinct above, and much contracted below. 
Facial suture marginal along a wide space in front, and below the eyes curved 
outwards, and ending on the posterior margin. Angles of head mucronate. No 
rostral shield. Wypostome? Axis of body narrow. Pleure without a furrow. 
Tail smooth with a moderately long axis. 
The flattened oval form, long axis to the tail, and head spines, very much re- 
semble Asaphus*, from which the 9 ungrooved pleurz effectually distinguish it. In 
the obliteration of the glabella, number of body-rings and course of the facial suture, 
it is closely allied to Il/enus, from which its habit differs so much ; but there is enough 
of the under side preserved to show that there was no rostral shield, an essential cha- 
racter of Jilenus. 
Species 1. Head spines short. 8. latifrons. Asaph. latifrons, Portlock, Geol. Rep., 
Tyrone, &c. pl. 7. figs. 5, 6. A. marginatus, ib. f.7.—Locality. Desertcreat, Ty- 
rone, in Llandeilo flags. 
Species 2? Head spines long. S.? Murchisona. Ogygia Murchisone, Murchison, Sil. 
System, pl. 25. fig. 3. Locality. Mount Pleasant, Caermarthen, in Llandeilo flags. 
The narrow axis and the smooth extremities of this species, as well as the apparent 
absence of eyes in the middle of the head, render it very probable that we have 
here a second species of the genus. The facial suture, too, as far as it can be traced, 
agrees with that of Stygina. 
The Chair of Kildare,.an interesting isolated patch of Llandeilo flags, discovered 
by Mr. Griffith, contains in some parts of the limestone swarms of a minute Trilobite 
belonging to the great group of the Olenide, but referable to no published type. It 
will soon be figured and described in Decade 7 of the Memoirs of the Geological Sur- 
vey. In the meantime the characters may be defined as follows :— 
Cyphoniscus, new genus. 
Gen. Cuar. Body oval and very convex; head large and gibbous; body of 7 seg- 
ments; tail minute. Head half-elliptical, the glabella occupying the greater part 
of it; glabella broadest in the middle, oval, and inflated, without lobes; neck- 
furrow distinct; cheeks bent steeply downwards, with nearly parallel sides, rather 
broadest below, the posterior angles square. Eye-line marginal in front for a space 
equal to the breadth of the glabella, then running in an oblique line down the cheek, 
and cutting the exterior margin very obliquely sume distance in advance of the pos- 
terior angle. Eyes (minute linear?) very forward; free cheeks narrow and linear. 
Thorax convex, the axis prominent, and the fulcrum of the pleurz near it. Pleure 
* One species of Asaphus, described by Portlock, 4. rectifrons, exactly resembles our genus 
in the wide marginal extent of the facial suture in front, and in the want of a vertical suture 
on the under side. But the eyes are in the usual position, and the blunt extremities and 
broad obscure axis show that this species is a true Asaphus, though probably not of the section 
Isotelus. 
