368 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



pointed posterior end than the juvenile specimens. The species is the 

 Vemis corMctiJa of Gmelin, 1792; Tivehi milgaris of Link, 1S07; Tri- 

 gonaradiata Megerle, 1811; Venns turgens {SoXundQV MS.) Dillwyn, 

 1817; Trigoiia fcisciataSch\xm2iCh(}\\ 1817, and the Cytherea corhiGula 

 of Lamarck, 1818. 



TIVELA (MACTROIDES var.?) NASUTA Dall, 1902. 



Santa Marta, Colombia; Baker. 



Having- the striped color pattern and tints of varieties of madroides^ 

 this shell has a very much more elongated form and more delicate 

 hino-e. There is nothing- in the collection which enables me to bridge 

 the gap between the two. 



TIVELA TRIGONELLA Lamarck, 1818. 



West Indies, and the Gulf of Paria. 



This little oval species appears to be rare. It is the Trigona angu- 

 liferaoi Gray, 1838, and perhaps the Cytherea in certa, Sowerby, 1851. 



TIVELA BRASILIANA Dall, 1902. 



West Indies; Santa Caterina, Brazil; Ihering. This form was at 

 first supposed to be T. hicolor Gra}^ but after study it was found to 

 differ, being a heavier and less angular. shell, with the dorsal slopes less 

 straight and the pallial sinus shorter and relatively smaller, though the 

 shell attains a greater size than T. hieolor. The type is from Brazil; 

 some young specimens from the Antilles appear to be the same. 



It is not at all certain that the T. diUwyni Deshayes, 1853 {T. inac 

 troides Sowerby, 1851), is not, after all, an extreme variety of mae- 

 troides Born; there is a specimen of T. hicolor Gv^j , in the collection, 

 marked as from Florida, but it is doubtless adventitious. 



TIVELA FULMINATA Valenciennes, 1827. 



Coast of southern Brazil at Rio and Santa Caterina. 

 Arcuate, with Ijrownish umbones and more or less zigzag tracery. 

 It has a length, when adult, of 60 mm. 



TIVELA (PACHYDESMA) VENTRICOSA Gray, 1838. 



Southern coast of Brazil. 



This fine species is figured from juvenile specimens in Romer's Mon- 

 ograph, and in all the manuals it is stated to come from China. Dr. 

 von Ihci-ing has repeatedly collected it from the coast of Brazil, and 

 the Chinese habitat is certainly erroneous. One specimen in the 

 United States National Museum measures 105 mm. in length, 00' mm. 

 in h(Mght, and 70 mm. in diameter. It is usually white with a dehiscent 

 vernicose periostracum. 



