ORDOVICIAN TRILOBITES FROM THE TOURMAKEADY LIMESTONE 
ETYMOLOGY. The pygidial spines droop in the style of a mous- 
tache. 
DIAGNOSIS. Occipital spine absent; L1 swollen and fully circum- 
scribed by deep S1; S2 deep and L2 with prominent inflation; 
librigenal field with large, coarse pitting; first pair of pygidial spines 
longest. 
HOLOTYPE. Pygidium It. 26059 (Pl. 10, fig. 6); paratypes It. 
26023-26058, 26060-26071. 
DESCRIPTION. Specimens of this taxon are so subject to varying 
amounts and vectors of distortion that relative cranidial dimensions 
are not meaningful. Anterior border relatively long (for subfamily), 
sculpture of numerous densely distributed fine tubercles; anterior 
margin with median part shaped like shallow inverted ‘v’ in plan 
view, with second distinct change in course in front of junction of 
axial and preglabellar furrow; anterior sections of facial sutures 
nearly straight, with considerable anterior convergence; axial fur- 
rows subparallel from SO to opposite S2, anteriorly convergent in 
front of L2 to grade smoothly into preglabellar furrow; axial and 
preglabellar furrows deep; small trapezoidal frontal area with sculp- 
ture similar to anterior border; eye ridge prominent, running obliquely 
from opposite L3 to front of palpebral lobe, subparallel with lateral 
margin, defined by furrows, anterior of which is deepest, seen best 
ventrally (Pl. 8, fig. 2b); palpebral lobe very narrow, posteriorly 
contiguous with small sutural ridge; posterior furrow of eye ridge 
grading into incised palpebral furrow, continued posteriorly along- 
side posterior sutural ridge; interocular fixigena broad (tr.) for 
subfamily, with tuberculate sculpture somewhat coarser than that of 
frontal area; posterior fixigena with significant area and lateral 
development, subtriangular, sculpture of moderate sized tubercles; 
posterior border furrow similar in depth to axial furrow, of same 
length (exsag.) adaxially and abaxially; posterior border with strong 
dorsal convexity, adaxial length similar to adjoining LO, becoming 
longer abaxially, sculpture of fine, evenly spaced tubercles similar to 
that of anterior border; prominent tubular spine running 
posterolaterally from fulcrum of posterior border; glabella strongly 
inflated, prominent sculpture of fine to coarse tubercles, coarse, 
_ closely spaced tubercles becoming predominant posteriorly; sagittal 
convexity of most specimens showing strong peak posteriorly in 
cone-shaped dorsal projection in front of LO; L1 fully isolated by 
deep S1; L2 slightly smaller than L1; S2 well impressed, but 
shallower than $1; smooth band present on many specimens around 
anterior edge of S1 and S2; L3 strongly defined; S3 short (exsag.) 
and with reduced transverse course, but still quite strongly incised; 
SO deep, of even length sagittally and exsagittally; LO quite short 
(sag., exsag.), dorsally convex (sag., tr.), and with dense tuberculate 
sculpture similar to rear of pre-occipital glabella; tiny fossula present 
in axial furrow opposite midlength of eye ridge (PI. 9, fig. 5b). 
Librigenal lateral margin with strong, even lateral convexity; 
lateral border about 40% of width (tr.) of librigena, broadly inflated, 
with sculpture of dense tubercles, finer anteriorly and laterally, 
becoming coarse posteriorly along lateral border furrow; lateral 
97 
border furrow broad and deep, shallowing abruptly both posteriorly 
and anteriorly, terminated anteriorly by very pronounced sutural 
ridge along anterior section of facial suture; field with large, irregu- 
larly distributed pits and mixture of large, coarse tubercles and 
greater number of fine tubercles; single exsagittal row of very fine 
tubercles beneath eye; eye small (Pl. 9, figs 14, 16); doublure 
slightly narrower than lateral border, essentially flat and smooth, 
narrowing slightly posteriorly. 
Rostral plate unknown. Hypostome with sagittal length about 
55% of maximum width (excluding anterior wings) across shoul- 
ders; moderately strong sutural ridge along hypostomal suture; 
anterior margin anteriorly convex with more abrupt change in slope 
sagittally, bowed anteriorly around anterior wings; middle body 
separated from sutural ridge by very short (sag., exsag.) furrow, 
sagittal length about 60% of maximum width, sculpture of very fine 
tubercles, slightly coarser anteromedially; middle furrow deep later- 
ally, running posteromedially, in some specimens shallowing but 
meeting sagittally to fully circumscribe anterior and posterior lobes; 
lateral border broad, with tuberculate sculpture slightly coarser than 
that of middle body; anterior wing tab-shaped, set at slightly oblique 
(30-45 degrees) angle; shoulder small but sharply protruded; lateral 
and posterior border furrows broad and very shallow; posterior 
border long (sag., exsag.), sculpture smooth, posterolateral corners 
lobate, embayed sagittally; doublure forming sharp dorsal fold and 
ridge around shoulder, lacking sculpture. 
Thoracic segments with large articulating half-ring, set off 
posteriorly by sharp break in slope; axial ring longer (exsag.) 
laterally, shortened sagittally, sculpture of dense, fine to moderate 
sized tubercles; axial ring separated from articulating half-ring by 
broad, long preannular lobe, always developed as a depressed area, 
never with independent inflation; axial furrow very shallow, ring 
nearly contiguous with pleura; pleura proximal to fulcrum com- 
posed of subrectangular base topped by semicylindrical rib; rib with 
prominent knob-like swelling on anteroproximal part, with shallow, 
oblique furrow set posterior to swelling (Pl. 10, fig. 4a); pleura distal 
to fulcrum composed of free, tubular spine, lengthening and more 
posteriorly inclined on more posterior segments, with dorsal sculp- 
ture of moderately sized tubercles. 
Pygidium composed of three segments, anterior segment with 
morphology essentially identical to that of posterior thoracic seg- 
ment; articulating half-ring separated from first axial ring by narrow 
furrow, preannular lobe absent; axial furrows subparallel and deep 
on first segment, very shallow on second, entirely effaced on third; 
first axial ring with robust tuberculate sculpture; second ring very 
short (sag., exsag.), with four or five tubercles of same size as those 
on first ring; ring furrow between first and second rings broad and 
deep, forming pit laterally; second ring furrow slot-like (Pl. 10, figs 
11a, 14a), in many specimens reduced to lateral pits (Pl. 10, figs 7, 
9); third segment expressed as pair of median spines united by small, 
tuberculate terminal piece; first spine pair elongate, posteriorly 
recurved; second and third pairs progressively shorter; all spines 
with dorsal and dorsolateral tuberculate sculpture similar in size and 
| PLATE 9 
| Figs 1-21 
Mayopyge zapata gen. et sp. nov. 1, It. 26034, cranidium, dorsal view, x6. 2, It. 26035, cranidial fragment, dorsal view, x10. 3a-b, It. 26036, 
cranidium, dorsal and left lateral views, x7.5. 4, It. 26037, cranidium, dorsal view, x7.5. 5a-e, It. 26038, cranidium, dorsal, ventral, and anterior views, 
x10. 6a-c, It. 26039, cranidium, left lateral, dorsal, and anterior views, x10. 7a-b, It. 26040, cranidium, dorsal and left lateral views, x7.5. 8, It. 26041, 
cranidium, dorsal view, x7.5. 9a-b, It. 26042, right librigena, external and internal views, x10. 10, It. 26043, left librigena, external view, x7.5. 11, It. 
26044, right librigena, external view, x7.5. 12, It. 26045, right librigena, external view, x10. 13, It. 26046, left librigena, external view, x7.5. 14, It. 
26047, left librigena, external view, x10. 15, It. 26048, right librigena, external view, x7.5. 16, It. 26052, right librigena, external view, x7.5. 17a-b, It. 
26049, hypostome, ventral and dorsal views, x7.5. 18, It. 26050, hypostome, ventral view, x10. 19, It. 26051, hypostome, ventral view, x7.5. 20, It. 
26053, hypostome, ventral view, x7.5. 21a-b, It. 26054, cranidium, oblique and posterior views, 7.5. 
