Citron de carmes pear appears to be an excellent pear that is not well known. You might be interested in this link https://npgsweb.ars-grin.gov/gringlobal/accessiondetail.aspx?accid=%20PI+541163. ARS GRIN states "Nomenclature of this variety is somewhat confused. Hedrick states that it has been known by no less than 50 different names. In France and England its official name is Citron de Carmes, but in America it has generally been recognized as Madeleine. Origin uncertain. Cultivated by Le Lectier in France as early as 1628. Fairly wide distribution in United States about 1830. Added to APS catalog list in 1848. Fruit small in size, roundish-obtuse-pyriform. Skin tender, fairly smoth, dull green in color, with numerous small dots. Flesh tinged with yellow, fine, melting, very juicy. Sweet, rich, vinous flavor. Among the earliest in season. Short-lived, subject to core breakdown if left on trees too long. Too tender to withstand shipping. Tree moderately vigorous, spreading in habit, grayish green in foliage, productive. Fairly susceptible to fire blight. – H. Hartman, Oregon Ag. Experiment Station, 1957.
Madeleine. Origin France? Ripens at the feast of St. Madeleine and first cultivated by the Carmelite Monks. Synonyms: Citron de Carmes, Citron des Carmes, Early Chaumontelle, Early Chaumontel (incorrectly), Early Madelaine, Early Rose Angle, Green Chisel (incorrectly), Grune Magdalena, Grune Sommer, Grune Sommer Magdalena, Hasting pear, Madeleine au Citron des Carmes, Madeline, Magdalen, Magdaleine, Magdelen, Poire Hativeau, Sainte Madelaine. – W.H. Ragan, Nomenclature of the Pear, 1908.
Madeleine, or Citron des Carmes (of John Lindley, 1828; Robert Thompson, 1842). Madeleine (of Louis Noisette, 1839), Citron des Carmes (of Duhamel, 1768), Magdelen, Green Chisel (incorrectly), Early Chaumontelle (incorrectly). The Madeleine is one of the most refreshing and excellent of the early pears; indeed, as yet, much the best at the time of its ripening - before the Bloodgood. It takes its name from its being in perfection, in France, at the feast of St. Madeleine. Citron des Carmes comes from its being first cultivated by the Carmelite monks. It is much the finest early French variety, and deserves a place in all collections. The tree is fruitful and vigorous, with long erect olive-coloured branches. Fruit of medium size, obovate, but tapering gradually to the stalk. Stalk long and slender, often nearly two inches, set on the side of a small swelling. Skin smooth, pale yellowish-green, (very rarely, with a little brownish blush and russet specks around the stalk.) Calyx small, in a very shallow, furrowed basin. Flesh wihte, juicy, melting, with a sweet and delicate flavour, slightly perfuned. Middle and last of July. – A.J. Downing, The fruits and fruit trees of America, 1846.
Citron de Carmes. This is a very fine early fruit - the size is small, not much larger than the Hativeau - the skin green, the flesh juicy, buttery, and highly flavored - the taste, when not too ripe, sugary. This pear Mr. Prince calls the early Chaumontel; it is one of the finest fruits of the season. – W. Coxe, A view of the cultivation of fruit trees, 1817."
I’ve only grown the pear for a year but I’m already excited to see how good the quality of the fruit will be in Kansas. The wood is a reddish brown color and very different from other pears. The background of some pears is obvious from the common traits but as mentioned this one shares no traits with any of my other pears.
You might also be interested in this link Medieval Cookery - Fruit Varieties which shows this picture of the pear
Photo - USDA National Germplasm Repository