B A R T E L E T T I A 



AND MULLERIA. 



Genus BARTELETTL\, Adams. 



Testa bimusculosa, suhcequivalvis, Wicra, ovato-suh- 

 trigona, irregularis, valde inccquilatcrali, intus 

 margaritacea. Area cardinalis hrevis. Ligamen- 

 tum in sulcum dispositum. Apices approximati. 

 Impressiones musculares distantes, antico perparvo. 



Shell bimuscular, subequivalve, free, ovately subtri- 

 gonal, irregular, very inequilateral, pearly within. 

 Cardinal area short. Ligament placed in a sulcus. 

 Apices approximate. Muscular impressions dis- 

 tant, tlie anterior one very small. 



The very curious species forming this genus was 

 first described by Moricand as an Etheria. But the 

 fact of its being a free and nearly equivalve shell, and 

 otherwise very singular in its structure, is sufficient to 

 justify its generic separation. It is an inhabitant of 

 the Eiver Amazon. Although distinctly bimuscular, 

 it may be considered, from the very small size of the 

 anterior cicatri.x, and from the great development of 

 the posterior side of the shell, as helping to bridge 

 over the passage from the Bimuscular as represented 

 by Etheria, and the Unimuscular as represented by our 

 nest genus, Mulleria. 



Species 1. (Fig. 2, a, h, Mus. Brit.) 

 Bakteletti.^ Stephanensis. Bar. testd trigono-stib- 

 reniformi, sulirregulari, antice attciiuatd, coarc- 



tatd, diffonni, costis tuherculiferis irregulanhus 

 rugatd ; medio ad marginem ventralem sinvatim 

 amtracto ; postice tumido, angulatim expanse, con- 

 centrice subnigato, txLberculis subobsoletis ; externe 

 epidermide olivaceo-fusco indutd ; marginibiis an- 

 ticis laqueatis ; vmbonibus regularibus, suhquad- 

 ratis, antice lix productis. 



SiEriiANsrs Bartelettia. Shell trigonal-subreniform, 

 rather irregular, anteriorly attenuated, contracted, 

 deformed, wrinkled with irregidar tuberculated ribs ; 

 in the middle sinuously contracted at the ventral 

 margin ; posteriorly tumid, angularly expanded, 

 concentrically somewhat wrinkled, with suliob- 

 solete tubercles; externally covered with an olive- 

 brown epidermis ; anterior margin fluted ; um- 

 boes regular, subquadrate, anteriorly scarcely 

 produced. 



MoKicAND (Etheria). Journal of Conchology, 1856, p. 

 178. 



Hub. River Amazon, South America. 



The umbonal region or nucleus of the shell presents 

 the appearance of a young cardita, with the anterior 

 side very small. Afterwards the shell becomes irre- 

 gular, slightly so at the posterior side, and very much 

 so at the anterior side, where it is much contracted, 

 and although produced only partially developed. The 

 anterior muscular impression is very small, and half 

 hidden under the thickened edge of the shell. 



