.353 



angular sides, deltidia rather large, separate ; mesial ridge very 

 slight ; ventral valve nearly orbicular ; internal a])pendage large, 

 Tths the length of the shell, formed as in T. Californica ; margin 

 *^f the valves entire. 



In the British Museum and in Mr. MetcaKe's Collection. 



20. Teuebuatula Uva (pi. Ixx. f. 53-55.) Broci. Zool. Proc. 

 1833, p. 124. 



Testa oblonga, gibbosa, glabra, subdiaphana, pallescente ; valvis 

 inrequalibus ; hnea marginali ex mnbouem ascendente, demuni 

 subtiexuosa ; valva dorsali posticc subelongata, apice reflexo, trun- 

 cato, foramine magno, integro, perobhcfuo, margine crasso; area 

 cardinaK inconspicua, rotundata ; deltidiis parvis, coalescentibus, 

 concavis ; carina mediana nulla ; valva ventrali ovato-oblouga, sulco 

 mediano nullo ; ossiculo interno parvo, radiis binis, ex cardinem 

 extensis, ad apices expansis efformato ; margine valvarum integro. 



Shell oblong, gibbous, smooth, shghtlj diaphanous, pale in 

 colour ; \^alves unequal ; marginal line ascending from the apex, 

 then somewhat fiexuous; dorsal valve posteriorly lengthened, 

 with a reflected, truncated apex; perforation large, entire, 

 very obKque, mth a thickened margin; cardinal area indistinct, 

 rounded; deltidia small, united, concave; ventral valve ovato- 

 obloug ; internal appendage formed of two rays setting off from 

 the hinge and expanded at the ends ; margin of the valves entire. 

 This species is destitute of mesial ridge and furrow. 



From the Gulf of Tehuantepec ; in IVIr. Cuming's Collection. 

 The punctulation in this species is much coarser than in T. vitrea. 



21. Tekebratula vitrea (pi. Ixx. f. 56-59.) Lam. 



Testa rotundato-ovata, ventricosa, subdiaphana, Igevissima, albi- 

 cante; valvis suba?qualibus, linea marginaK rectiuscula ; valva 

 dorsali postice rotundato-subacimiinata, recurva ; foramine parvo, 

 integro, subobliquo, margine crasso ; area cardinali inconspicua, 

 rotundata ; deltidiis inconspicuis, coalescentibus ; carina mediana 

 nulla; valva ventrali subcirculari, antice rotundato-subtruncata, 

 sulco mediano mdlo ; ossiculo interno parvo, \ longitudinis testae, 

 antice arcuato, fornicato ; margine valvarum integerrimo. 



Shell of a rounded ovate form, ventricose, slightly diaphanous, 

 very smooth, wliitish horn colour, valves nearly equal and marginal 

 line nearly straight ; dorsal valve rounded and slightly acuminated 

 behind, recurved; perforation small, entire, rather obhque, with a 

 thickened margin ; cardinal area indistinct, rounded, with united 

 indistinct deltidia ; ventral valve nearly circular, shghtly truncated 



