« Shell broadly rounded to elongate; moderately sized to minute; thin to moderately thick; subequivalve; subequilateral to strongly inequilateral; compressed to very inflated; sculpture usually of commarginal striae, some with radial striae or ribs, few with strong commarginal ribs; umbones minute to prominent, prosogyrate to opisthogyrate, submedial to posterior; prodissoconch minute to large, well demarcated in some; periostracum thin, usually translucent; hinge plate variable, frequently with at least one strong cardinal tooth; right valve frequently with strong lateral teeth, fitting into grooves in left valve; ligament usually internal, oblique, in small to large resilifer; dimyarian… » – Coan & Valentich Scott: Bivalve Seashells of Tropical West America, Santa Barbara 2012, p. 493.
 

Shell equivalve, « transversely trigonal to trapezoidal, slightly inequilateral, flattened, shining, smooth or with faint infra-externally placed radials, crenulating inner margin. Hinge with narrow, oblique well marked cardinal teeth 1, 2a, 2b, and traces of lateral teeth AIII, AII in front of them; short well defined resilifer and moderately strong lateral tooth PI, strong PII, traces of PIII, all closely behind ligament. » – Hoeksema & Simons: “Bornia canariensis, a new species from the Canary Islands” Basteria vol. 75 p. 32.
 

« Shell very small, obliquely oval in outline, inequilateral, beaks towards the posterior. Sculpture of concentric raised threads some dichotomizing. Ligament large, internal; resilifer shallow, slightly sterior to beaks. Right valve with single anterior and posterior lateral teeth; left valve with marginal flanges, single small tubercle beneath and slightly to the anterior of the beak. » – Holmes, Gallichan & Wood: “Coracuta obliquata n. gen. (Chaster, 1897) (Bivalvia: Montacutidae) - First British record for 100 years.” Journal of Conchology vol. 39(2) p. 151.
 

Shell minute, « fragile, equivalve and somewhat compressed, inequilateral, anteriorly extended, ovate or subtrapezoidal, with maximum length ventral to mid-height giving a somewhat dorsally angulate appearance. White or pale fawn in colour, with fine irregular commarginal growth lines and, in some species, faint radial lines. Hinge plate with elongate anterior and posterior lateral teeth in each valve, single slightly oblique cardinal tooth anterior to umbo in each valve, the left cardinal usually smaller than right. Internal ligament, ventral and posterior to umbo, with a fine, barely visible external ligament present in some species. » – J. A. Allen: “A new deep-water species of the genus Epilepton (Bivalvia : Galeommatoidea) from the Atlantic” The Veliger vol. 49(1), Berkeley 2007, p. 7.
 

Shell minute, equivalve, slightly inequilateral with a round posterior margin and a little less obtuse anterior side (anterodorsal margin less arched than the posterodorsal). The genus is, at this time, monospecific.
 

« Shell somewhat globular, equivalve, closed. Hinge with two approximate teeth and a remote lateral tooth in one valve, and a concave tooth and remote lateral one in the other. Ligament internal. The genus is denominated from our worthy and scientific fellow-student in this department of science, J. M. O’Kelly, Esq. of Dublin. » – W. Turton: Conchylia insularum britannicarum, London 1822, p. 57.
 

« Shell small, somewhat longer than high and moderately inflated, equivalve, inequilateral with beaks within the posterior half. Prodissoconch lens-shaped, not very inflated, with or without a differentiated prodissoconch 2. Dissoconch with a sculpture of fine commarginal lines and, more rarely, radial microsculpture of indistinct divergent striae. Ventral margins of valves smooth and tightly appressed. Cardinal platform extending dorsally on either sides of beaks, over approximately half of the shell length, interrupted beneath the beaks by a notch in which is lodged a large internal ligament. Lower part of ligament with small calcified portion constituting a lithodesma. Left valve with indistinct laterals, one anterior and one posterior, usually expressed as mere swelling of cardinal platform; right valve with two short but very distinct laterals bordering ligament anteriorly and posteriorly, separated from dorsal margin by distinct grooves, their termination bulging ventrally from cardinal platform. Anterior and posterior muscle scars subequal. Pallial line thick, irregular, entire. Shell colour white on dissoconch, white or brownish on prodissoconch. » – Gofas & Salas: “A review of European ‘Mysella’ species”, Journal of Molluscan Studies vol. 74(2), Oxford 2008, p. 121.
 

Synonym Poronia Récluz, who writes: « I propose the genus Poronia for small bivalve shells which have relations on one side with Amphidesmas, Erycinas and Bornias and on the other side with Kellia Turton and Chironia Deshayes, but which nevertheless have sufficient distinctive characters so that it is possible to clearly differentiate them from all these genres. This is how the Poronias are distinguished from the Amphidesmas and Erycinas (Lamarck. Desh. Non Sowerby), not only by the shape, the position of their spatula and their cardinal teeth, but also by the impression of the mantle which is simple, while it is deeply winding in the Amphidesmas and Erycinas. They differ from Bornias, whose pallial impression is simple, by a very elongated ligamentous spatula, decurrent and bordering the internal surface of the lateral tooth, in all its extent; by their anterior, large, concave and ascending, cardinal tooth, double or penetrating on the other valve, and by the strong, triangular, spread and penetrating lateral tooth on the opposite valve; thus no confusion can exist between the two genera. » – C. A. Récluz: “Monographie du genre Poronie”, Revue Zoologique vol. VI, Paris 1843, p. 166.
 

« Shell flat, nearly orbicular, equivalve, inequilateral, a little open at the sides. Hinge of one valve with a single tooth and transverse linear lateral on each side; of the other valve with a cavity in the middle and a transverse deeply cloven lateral tooth each side, the segments of which divaricate from the beak. Ligament internal. » – W. Turton: Conchylia insularum britannicarum, London 1822, p. 62.
 

« Shells ovate, partly transparent, anterior region longer than posterior. Valves rather compressed, somewhat produced anteroventrally. Hinge flat, broad, each valve with single narrow protruding cardinal and distinct anterior and posterior laterals. Behind cardinal tooth, single hollow and oblique oblong resilifer » – Lützen & Kosuge: “Description of the Bivalve Litigiella pacifica n. sp. (Heterodonta: Galeommatoidea: Lasaeidae), Commensal with the Sipunculan Sipunculus nudus from the Ryukyu Islands, Japan”, Venus vol. 65(3), 2006, p. 194.
 

« Shell oval or oblong, equivalve, inequilateral, mostly closed. Hinge with two teeth in each valve, and a cavity between them; lateral teeth none. Ligament internal. In this genus there is a vacant space in both the valves between the teeth, causing them to be rather remote from each other. One of the teeth is generally concave or inclining to spoon-shaped. » – W. Turton: Conchylia insularum britannicarum, London 1822, p. 59.
 

At this time, the genus is monotypic. It was built for a species that lives exclusively in the nest of the worm Phascolion Théel, 1875. Shell small, equivalve, more or less equilateral (slightly expanded anteriorly), rectangular in shape, thin, with numerous uneven commarginal growth-marks, and no radial sculpture. Ventral margin more or less concave.
 

Shell equivalve, often very inequilateral with the anterior part elongate; ventral margin almost straight, dorsal margin angular, concave anteriorly; one big and one small cardinals in each valve, the laterals very reduced. The genus is attached to the substratum by some byssal threads projecting from a slight ventral embayment of the valves. Presence of some radial sculpture, especially in young specimens.
 

« Shell transverse, subovate, equivalve, inequilateral, shorter posteriorly. Cardinals: one or two minute. Laterals obsolete, lamellar. Ligament double: externally fibrous, minute; internally cartilaginous, inserted into an oblong pit. Two muscular prints, weak, subequal, rounded; pallial line simple, devoid of sinuosities. » – R. A. Philippi: Enumeratio molluscorum Siciliae… vol.2, Halle 1844, p. 27.
 

A synonym is Tellinomya Hall, 1847, whose description, erroneous and incomplete, was corrected in an ulterior article, published in 1856, in which one reads: « Shell equivalve, equilateral or subequilateral, closed, smooth or marked by lines of growth; ligament external; hinge line curved, sometimes sub-angular, with a continuous series of small curved transverse teeth, which diminish from the extremities to the beak, beneath which they are much smaller; muscular impressions double, two anterior and two posterior, one large and strongly impressed, the other smaller, lying above and between the larger one and the hinge line; pallial impression simple. » – J. Hall: “On the Genus Tellinomya, and allied Genera, with illustrations”, The Canadian Naturalist and Geologist vol. I(5), Montréal 1856, p. 391-392. Nota bene that the present shells are more than subequilateral: they are markedly inequilateral.