26 
Trigonia nasuta, Eth. fil., (leol. Pal. Q’land, &c., 1892, p. 567. 
TrUjonia mesemhria, Eth. fil., Gcol. Pal. Q’land, &c., 1892, p. 470. 
f Trigonia SJ). ind., Eth. fil., Geol. Pal. Q’land, &c., 1892, t. 26, f. 5. 
Sp. Char. — Shell (right valve) cleltoid-seaphoid, inclined to prow- 
shaped, inneh produced posteriorly, generally rather tumid. Cardinal 
margin highly arched, short and convex anteriorly, longer and somewhat 
concave posteriorly, ventral umrgin well rounded anteriorly, becoming 
rapidly oblique towards the posterior, with a cinctural inflection, and destitute 
01 denticles. Anterior end fairly rvell developed, Avithont any marked 
anterior slope, and the margin rounded ; posterior end produced, nasute, 
traversed by an oblique shallow cincture, widening toAA'ards the ventral 
margin ; posterior slope concave, delined from the cincture by three sharp 
keels, the narrow space between the Iavo anterior battened, hut hetAveen the 
median and the posterior there is a aatII defined groove. Umbonal region 
prominent and high, convex, hut not markedly tumid ; umho small and 
depressed ; escutcheon long, moderately Avidc and striate ; ligament strong. 
Cardinal teeth very large and strong, on both sides of the anterior tooth are 
lifteen transverse denticles, the inteiwening sulci Avider than the denticles ; 
dental crest elevated and sharp ; dental support very strong and thick ; on 
the upper and loAA^er aspects of the posterior tooth there are about thirteen 
denticles. Anterior adductor scar oval, of moderate size, bounded liy the 
thick dental support of the anterior cardinal tooth ; posterior adductor scar 
transversely elongate and shalloAA'; pedal scar not aa’cII defined (in specimen) ; 
siphonal grooA'es shalloAA" ; pallial impression not debned (in sjiecimen). 
Interior highly nacreous. Test thick, of two principal layers, the outer the 
thicker. Sculpture of regular equidistant concentric rugae, separated by 
Avider A^alleys, the later concentrically striate, the strirn passing across the 
cincture to the exclusion of the rugae ; no tubercles (outer shelly layer on 
the posterior slope not preserved). 
Ohs. — Tlie advantage gained by a study of the Rev. J. E. T. W oods’ 
type, leads to the opinion that the latter is identical Avith Mr. Etheridge’s 
Trigonia nasuta, notAAnthstanding the latter AA^as based purely on internal 
casts alone. I believe the latter to have been a cinctured shell, the anterior 
edge of the cincture being shown on the umboual region of Mr. Etheridge’s 
Eig. 2, at the break of the sculpture. I have eansed an internal cast of the 
present valve (PI. V, Eig. 3) to be prepared, and this AAnll exemplify hoAV 
closely the internal structure of Woods’ T. mesemhria ajiproaehes the natural 
