144 BRITISH PALAZOZOIC FOSSILS. [CrusTacra. 
Genus. TRINUCLEUS (Murch.) 
= Cryptolithus Green. 
Gen. Char.—Cephalie shield semicircular, the limb broad and flat, with several rows of impressed 
cup-like puncta on both surfaces; spines of the external angles very long; g/abel/a pyriform, without lateral 
furrows ; checks spherical triangles without eyes or eye-lines; generally a small spine on the neck furrow ; 
thorax of six joints, lateral lobes twice the width of the axis, flat, straight, with parallel sides, slightly 
deflected at their free ends, pleural groove broad, shallow, not reaching the margin; pygidiwm triangular 
with a deflected margin, axis with about seven segmental furrows, sides flat with about six segmental 
divisions each subdivided by a faint line towards the end. 
I have (Synopsis of Sil. Foss. of Ireland) drawn attention to a particular (7 antennary) pore in this and 
other genera of Trilobites near the front margin on each side of the glabella, in the furrow which separates the 
latter from the cheeks; in the same furrow I often observe in certain states of preservation two or three 
punctures on each side of the base, one of them in the neck furrow, indicating apparently the insertion 
of the oral muscles, and holding the place of the segmental furrows of other Trilobites. 
The facial suture of this genus as figured by Burmeister, on the authority of Loven, was supposed 
to go round the edge of the punctated border, to turn in at the angles, and cut the posterior margin 
near the angles of the cheeks; this would be so singularly unusual a course, that I have taken every 
pains to investigate the point, and feel satisfied there is no suture in the position indicated; on the other 
hand, I think I have ascertained their true course, in several species, to be in a more normal position ; 
as I have observed them, they run from the re-entering angles between the front of the glabella, and the 
cheeks close outside the furrow which separates the glabella from the cheeks nearly to the posterior 
margin where it turns outwards, (and may generally be well seen at this point) and runs parallel with, and 
a little above the posterior margin which it finally cuts near the outer angles of the cheeks. I have 
discovered a facial suture in precisely the same position in Ampyzx, the proximity to the furrow of the 
side of the glabella having probably caused them to be overlooked in both genera. 
TrinucLEeus Caractact (Murch.) 
Ref.—Murch. Sil. Syst. Pl. 23. f. 1. and Port. Geol. Rep. Pl. 1. B. fig. 3 and 5. 
Sp. Ch,—Cephalic shield nearly semicircular, its width exceeding twice its length; margin wide, regularly 
rounded, three concentric rows of punctures in front of the glabella, five rows in front of the cheeks, 
more numerous and scattered towards the angles, which have a triangular extension backwards and 
outwards, nearly half as far as the pygidium before giving off the slender spines which extend obliquely 
outwards and backwards; glabella smooth, broad, ovate, moderately gibbous; neck furrow strong with a 
small spine on the middle ; cheeks gibbous, smooth, triangular, their length and width about equal ; 
pygidium nearly as long as the abdomen, three times wider than long, slightly and obtusely mucronate, 
lateral lobes with five to eight furrows, the three first most distinct, axis with about fourteen minute segments. 
I agree with Col. Portlock in thinking this species has never more than three rows of pores in front 
of the glabella, I therefore believe it distinct from the Bohemian 7. ornatus which has always five; but 
besides the greater width of the punctured border in the 7’, ornatus it is fully distinguished from our species 
by the few furrows on, and the extremely small size of, the pygidium, which in the 7. Caractaci nearly 
equals the abdomen in length, but is only half that in the 7. ornatus. (See the figure of Beyrich, 
Untersuchungen iiber Trilobiten, Pl. 4. fig. 1, and the description of the same under the name 7. Goldfussi 
in Barrande’s “‘ Notice Préliminaire,” Ge. p. 31). 
Position and Locality—Alt yr Anker, Meifod, Montgomeryshire; Llechwedd, Llwyd, W. of Llan- 
fechan, Montgomeryshire ; Pwllheli, Caernarvonshire; Craig y beri, Llanarmonfach, Montgomeryshire ; Tan 
y Bwlch y Groes, S. of Bala, Merionethshire; Hordely 8.; Gelli Grin, Bala, Merionethshire ; Llanwddyn in 
the Berwyn Mountains; Rhiwargor, near Llanwddyn; Chiney Longville, Shropshire. 
