— 18n — 



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 distinctissinia, crenata; callus 

 humeralis crassissimus, ultra medium productus, dimi- 

 diam faci ei intern ae occupans; margarita rosacea. 



Long. 92, alt. 45, crass. 32 mm. 



Hab. in flumine Medjerda Tunisiae. 



Unio Medjerdae n. sp, 



Concha elongato-ovata, valde inaequilatera, solida, pon- 

 derosa, ruditer striata, olivaceo-nigrescens; margo 

 superior arcuatus, ascendens, inferior strictiusculus, 

 pone medium subretusus, anterior compressus, oblique 

 in inferiorem desinens, posterior in rostrum breve 

 depressum desinens. Umbones ad Vs longitudinis siti, 

 tumidi, antice rectangulatim truncati, depressi, contigui ; 

 ligamentum crassum elongatum, sinu brevissimo; 

 lunuia 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 crassac, elatae, dextra 

 cultellata; impressiones musculares anteriores pro- 

 fundae, sat magnae, subintrantes, posteriores super- 

 ficiales; impressio pallearis distincta, crenulata; callus 

 humeralis crassus, marginem inferiorem totum occupans; 

 margarita carnea. 



Long. 84, alt. 48, crass. 32 mm. 



Hab. in flumine Medjerda Tunisiae. 



