322 THE PEA EL Y FRESH- WA TEll M USSELS—SIMPSOX. vol. xviii. 



the left valve is dorsally winged, while tlie right is not. I have not 

 seen any of these singular shells, but from the lignres and descriptions 

 I should think the genus was a valid one, and that it belonged with 

 the Mutelidie. It was proposed for B. anceyi, by Bourguignat. 



Chamhardia of Bourguignat, a new name for the Egyptian Iridinas,^ 

 probably contains nothing which can not be satisfactorily placed in 

 other genera. The publication in which the genus is proposed is not 

 accessible to me. All the foregoing genera of Mutelidie are from 

 Africa south of the Sahara desert, with the exception of the Mle, which 

 is peopled with these forms to the Mediterranean. Some of the species 

 extend south into the Cape region. 



Genus GLABARIS, Gray.^ 



This generic name has been adopted by the Adams Brothers, von 

 Ihering, and others, for South American Naiades with edentulous hinges, 

 which had until 1847 been placed in Anodonta. So far as I know, no 

 true Anodontas are found south of Mexico, all the Central and South 

 American forms I have seen being undoubtedly members of the genus 

 Glaharls. The shells of this group, though resembling those of Ano- 

 donta in the fact that they are without teeth, are really (juite distinct, 

 and when once the differences are understood, there need be no diffi- 

 culty in distinguishing them. 



The shells of Glabaris are usually of more solid structure than those 

 of Anodonta, and some of them are covered with the j)eculiar clothlike 

 epidermis which is found on a number of the Monocondyljeas. The 

 nacre is of a peculiarly soft, often brilliant and iridescent texture, in 

 strong contrast to the lusterless interiors of most of the Anodontas. In 

 a few of the species typified by G. tenehricosa^ it is a sort of lurid greenish 

 hue, but in these its tints are soft and rich. Frequently slightly ele- 

 vated rays reach out from the cavity of the beaks, especially in those 

 with the brightest nacre. There is in nearly all cases a well-defined and 

 tolerably broad border of the prismatic layer shown around the inside 

 of the shell, which is generally darker in tint than the nacre, and often 

 semi-transparent. In the G. lato-mnryinata group this is especially dark 

 ajid broad, being often as much as a quarter of an inch in width. It is 

 caused by the fact that the mantle does not deposit nacre to the border 

 of the shell. Traces of taxodont teeth have been noticed in some of the 

 South American species by v. Ihering and the writer, and these are 

 sometimes j)resent in G. granadensis of Nicaragua. 



According to d'Orbigny,^ Iridina {Glabaris) trapesialis, Lamarck, and 

 other allied species, are characterized by having distinct siphons, while 

 in G. membranaeea, Orbiguy, which probably is the same as G. lato- 

 marginata, Lea, the borders of the mantle are free at the siphonal 



1 Bourguignat, in Servain, Bull. Soc. Mai. France, VII, pp. 304-315, 1890. 

 '^Proc. Zool. Soc, London, 1847, p. 197. 

 3Voy. Amer. Mcrid., pp. 596, 617. 



