22 
Tate — List of Irish Liassic Fossils. 
24. Ceromya gibbosa, Etheridge , Quart. Jour. Geol. Soc., Vol. xx., p. 112, 
figs. 3-4 (1863). 
Isocar dia Elea, D’Orbigny, Prodromus, Vol. 1., p. 218 (1850). 
s .‘ Shell ventricose, deep, especially at the umbonal region. Umbones small, 
sub-central, slightly curved or involute, leaving a wide and exposed lunular 
region, strongly marked by concentric ridges of growth. Anterior side pro- 
duced, rounded and gaping. Posterior side attenuated, slightly truncate. 
Ventral margin much produced, giving the shell a nearly circular appearance. 
Height, 1 7 inch; depth, 1*3 inch; length, 2‘i inches.” — Etheridge. 
The specific identity of C. gibbosa, Etheridge, with Isocardia Elea , d’Orbigny, 
results from a comparison of the type specimens ; the diagnosis of the latter is 
so imperfect as to claim no consideration from palaeontologists. It is as follows: 
— “ Grosse espece bombee, triangulaire lisse, a crochets contoumes.” 
Geological Position. — Zone of “A. angulatus,” Island Magee, Co. 
Antrim; not rare ( Gray, Tate); Cotham, Bristol ! (Napier); “ A . Bucklandi ” 
Zone, Lyme Regis ! (Coll. Geol. Soc.) ; Lower Lias, Langres, Haute-Mame ! 
( D' Orbigny. ) 
25. Thracia ^equata, nov. spec. 
Shell transversely oval, ventricose ; umbones medial, obtuse ; hinge line 
angulated ; anterior extremity rounded ; posterior extremity moderately ob- 
liquely truncated ; a very faint keel proceeds from the umbo to the postero- 
ventral margin, ornamented with furrows and close set fine striae^ coincident 
with the ventral margin, which is arched. Breadth, '55 inch ; length, ‘4 inch; 
thickness, '25 inch. 
It has much the shape of T. lata, Munster, from which it is distinguished 
especially by its ventricosity and curved front margin. 
The genus Thracia has not yet been catalogued from English strata, 
older than the Inferior Oolite, and, indeed, if Myacites ?nactroides , Schlo- 
theim, of the Lias, be not a Thracia, then the genus has till now been 
unknown below the Middle Lias. T. rugosa, Dunker, a Lower Lias shell, 
is considered to be a Pleuromya , and has been re-described as such under 
the name of P. Dunkeri, by Terquem, so that T. cequata is, at the present 
time, the oldest British example, if not the oldest-known species of the 
genus. I take this opportunity to announce the discovery, by Mr. E. 
Welford, of T. glabra, Agassiz, in the Upper Lias Clay at Eydon, where it 
was found associated with Leda ovum, Inoceramus dubius, and other species, 
which serve to fix its stratigraphical position in the Zone of “ Ammonites 
communis. ” 
Geological Position. — Zone of “A. angulatus, ” Waterloo, Larne. Speci. 
men unique. ( R . T. ) 
26. Anatina myacina, nov. spec.. Plate I. fig. 16. 
Shell oblong, elliptical, umbones sub-central, small, ventricose, recurved 
