— 15 — 
dextrae crassus, pyramidalis, postice incisione distincta 
triangulari a margine cardinali dilatato sejunctus, dentes 
valvae sinistrae compressi, crenati, sulco angusto di- 
visi, sed divergentes, anterior subduplex; lamellae 
humiles, solidae; impressiones musculares anteriores 
magnae, profundae, subintrantes, posteriores super- 
ficiales; linea pallearis distinctissima, crenata; callus 
humeralis crassissimus, ultra medium productus, dimi- 
diam faciei internae occupans; margarita rosacea. 
Long. 92, alt. 45, crass. 32 mm. 
Hab. in flumine Medjerda Tunisiae. 
Umio Medjerdae n. sp. 
Concha elongato-ovata, valde inaequilatera, solida, pon- 
derosa, ruditer striata, olivaceo-nigrescens; margo 
superior arcuatus, ascendens, inferior strietiusculus, 
pone medium subretusus, anterior compressus, oblique 
in inferiorem desinens, posterior in rostrum breve 
depressum desinens. Umbones ad Y, longitudinis siti, 
tumidi, antice rectangulatim truncati, depressi, contigui; 
ligamentum crassum elongatum, sinu brevissimo ; 
lunula rhomboidea brevis, inter umbones vix intrans. — 
Cardo sat fortis; dens valvae dextrae crassus, sub- 
compressus, rotundato-triangularis, crenatus, fossula 
distincta sat profunda antice, et incisione distincta 
a margine cardinali sejunctus, dentes valvae sinistrae 
approximati, subcompressi, fovea cardinali laterali vix 
discreti, subdivergentes; lamellae crassae, elatae, dextra 
cultellata; impressiones musculares anteriores pro- 
fundae, sat magnae, subintrantes, posteriores super- 
ficiales; impressio pallearis distincta, erenulata; callus 
humeralis crassus, marginem inferiorem totum oceupans; 
margarita carnea. 
Long. 84, alt. 48, crass. 32 mm. 
Hab. in flumine Medjerda Tunisiae. 
